CompTIA A+ 220-1001A Lesson 3

Triple Layer BD

- 100GB - BD-XL specification

Dual Layer BD

- 50GB, readable in regular drives

Blue-Ray Disc (BD) mini-discs

- 8cm, can store 7.8gb per layer

dual-channel memory

- two pathways through the bus to the CPU, meaning that 128 bits of data can be transferred per "transaction" rather than 64 bits. this still increases the bandwidth available. (that is, there are no "dual-channel" DDR memory modules). - Motherboard DIMM slots (dual channel). Slots 1 and 3 (black slots) make up one channel, while slots 2 and 4 (grey slots) make up a separate channel.

Memory Cards

- type of flash memory - used extensively in consumer digital imaging products, such as digital still and video cameras. There are several proprietary types of memory card. -Secure Digital(SD), Mini-SD, Micro-SD, Compact Flash (CF), xD - Note: The speeds quoted are "max burst speed." Sustained read and write speeds will be much lower. Cards also have a speed class rating indicating their minimum write speed capability. - Note: The smaller form factors can be used with regular size readers using a caddy to hold the card.

Software RAID

-Windows provides the option to set up software-based RAID using standard disks and controllers. -Windows Server and Windows client Professional/Enterprise editions support fault tolerant mirroring (RAID 1) and striping with parity (RAID 5) arrays. -In a software solution, internal disks using different types of interface can be combined in an array but USB- or Thunderbolt-connected external drives are usually not supported. -All editions of Windows 10 come with the Storage Spaces feature, which provides mirroring and parity-based RAID-like functionality with USB-connected and other external drive types. -Linux® can use the Logical Volume Manager (LVM) to implement most RAID levels. to implement most RAID levels.

DISK INTEGRITY TESTING

-You can use the Windows chkdsk utility to verify the integrity of a formatted disk. Most hard drives run a self-diagnostic program called S.M.A.R.T (Self-Monitoring, Analysis, and Reporting Technology) t. In Windows, you can run the following command to perform a S.M.A.R.T check: wmic /node:localhost diskdrive get status -If you suspect that a drive is failing, you should try to run more advanced diagnostic tests on the drive. Most hard drive vendors supply utilities for testing drives or there may be a system diagnostics program supplied with the computer system.

Digital Versatile Discs (DVD)s

-delivers substantially more capacity (up to about 17 GB). DVDs are used for software installs and for games and multimedia. -higher densities than CDs, DVDs are also thinner and can be dual-layer (DVD DL) and/or double-sided (DVD DS). -higher transfer rate, with multiples of 1.32 MBps (equivalent to 9x CD speed). -fastest models = 4x read and write speeds. - DVDs, referred to as DVD-R/DVD-RW versus DVD+R/DVD+RW. Most drives can read all formats but write in either + or - format. Many consumer DVD players can play DVD±R discs. -650 nm red laser

Redundant Array of Independent Disks (RAID)

-many hard disks can act as backups for each other to increase reliability and fault tolerance, or they can act together as one very large drive. - When building a RAID array, all of the discs should be identical however this is not mandatory Note: RAID can also be said to stand for "Redundant Array of Inexpensive Disks" and the "D" can also stand for "devices."

Host Bus Adapter (HBA)

provide a connection point for internal mass storage devices, such as hard drives, optical drives, and tape drives. The interface between the drive, host adapter, and the rest of the system is a type of bus. - 2 main bus standards: Parallel ATA (PATA), Small Computer System Interface (SCSI) but these have been replaced by SATA - Note: HBAs are also commonly referred to as drive controllers. Technically, the controller is the circuitry in the disk unit that allows it to put data on the bus, which the HBA shuttles to the CPU or RAM.

Drive enclosure

provides USB, Thunderbolt, and/or eSATAp ports. The enclosure also provides for an external power supply if needed

BD-RE

re-recordable

bootrec /fixboot

repairs boot sector

Mirroring

requires at least 2 discs, the mirror disc is a duplicate of the data disc

DVD Drive

similar to a CD drive, but with a different encoding method and a shorter wavelength laser. -feature a higher transfer rate, with multiples of 1.32 MBps (equivalent to 9x CD speed). - fastest models feature 24x read and write speeds. Note: Most DVD drives can read and burn both DVD and CD media. When DVD was first introduced, drives that could burn CDs but only read DVDs were referred to as combo drives.

parity checking

simple error detection method used by motherboards - Each byte of data in memory is accompanied by a ninth bit. This bit is set to 1 or 0 to make the total number of bits set to 1 in the byte an odd or even number, When the byte is read, its parity is checked to ensure that the parity value is still odd (or even). If this is not the case, a bit must have become corrupted.

Mini-SD

smaller version of the SD card, using the same capacity and speed designations.

Micro-SD

smallest version of the SD card, using the same capacity and speed designations.

Serial Advanced Technology Attachment (SATA)

standard means of attaching internal storage drives to a desktop PC. It has superseded the legacy Parallel ATA (PATA) technology. - cables up to 1m - 7-pin connector - hot swappable - 1st standard up to 1.5GBps - 2nd revision up to 3Gbps - 3rd revision = 6Gbps

Disk striping

technique where data is divided into blocks and spread in a fixed order among all the disks in the array.

chkdsk/r

tests surface of a hard disk, if bad sectors are located each time this is run it is a sure sign that the disc is about to fail

Hybrid Drive

the SSD portion functions as a large cache, containing data that is accessed frequently. The magnetic disc is only spun up when non-cached data is accessed. Version 3.2 of the SATA standard defines a set of commands to allow the host computer to specify how the cache should be used (also referred to as host-hinted mode). Alternatively, the drive firmware can run self-optimizing routines. The user does not have direct control over files stored on the cache.

bootrec /rebuildbcd

to add missing Windows installations to the Boot Configuration Database (BCD

GDDRx

type of DDRx optimized for use on graphics cards.

File Recovery Options

-remove the drive from its internal enclosure and connect it to another PC. -Use a screwdriver that matches the type (flat, crosshead/ crosspoint/Phillips, or star/Torx) and size of screw to avoid damaging the screw heads or threads. -External enclosure kits are available to provide the data and power connectors required. -The enclosure will be interfaced to the PC via a USB port and the disk can be mounted using Disk Management (if it is in a state to be recognized by Windows) or analyzed using file recovery software. -If a file is corrupted, it may be possible to use software to rebuild it (or at least, to recover some data from it). -chkdsk restores file fragments from bad sectors to the root of the volume (as filennnn.chk files), but these are rarely directly usable. Third-party file recovery software is available

RAID 0 (striping without parity)

-requires at least two disks. -advantage is to improve performance by spreading disk I/O over multiple drives. -The logical volume size is the combined total of the smallest capacity physical disk in the array. - all the disks should normally be identical but this is not mandatory -If disks are different sizes, the size of the smallest disk in the array determines the maximum amount of space that can be used -RAID 0 adds no storage overhead and is a means of obtaining a large logical volume from multiple, low capacity disks. -this method cannot be said to be a true RAID implementation because it provides no redundancy If any physical disk in the array fails, the whole logical volume will fail, causing the computer to crash and requiring data to be recovered from backup. C -consequently, RAID 0 would never be used for live data storage.

CD-RW

-rewritable disc format - uses a heat sensitive compound whose properties can be changed between crystalline and amorphous by a special laser

Compact Flash (CF)

-supports 512 GB, though - no cards larger than 256 GB were ever made. -speed of CF cards is rated on the same system as CDs, using multiples of 150 KBps. -fastest devices work at up to 1066x read speeds (or 160 MBps).

Master Boot Record (MBR)

-the MBR is located in the first sector of the first partition. -contains information about the partitions on the disk plus some code that points to the location of the active boot sector. -The Boot Sector is located either on the sector after the MBR or the first sector of each other partition which describes the partition file system and contains the code that points to the method of booting the OS (the Boot Configuration Data store for a Windows system, or GRUB or LILO Linux boot managers). -Each primary partition can contain a boot sector, but only one of them can be marked active.

Secure Digital (SD) card

-three capacity variants. The original SD cards have a -2 GB maximum capacity in original cards -up to 32 GB in SDHC -SDXC is up to 2 TB. There are also four speed variants. -25 MBps = original speed - UHS allows up to 108 MBps, - UHS-II is rated at up to 156 MBps full duplex or 312 MBps half duplex, - UHS-III specifies two full duplex rates of 312 MBps (FD312) and 624 MBps (FD624).

PREPARE A HARD DISK FOR USE

1.If this is the first drive in the system, you will need to install an operating system. If you are installing an additional hard drive, you can use Disk Management to prepare the new drive. a.Log on to Windows. b.Open Computer Management. c.In the left pane, select Disk Management. d.Right-click the new disk, and select New Partition. Partitioning the drive defines one or more discrete storage areas on the same physical disk. This is useful for installing multiple operating systems or for defining system and user data storage areas. e.Follow the New Partition wizard prompts to partition and format the new drive. f.Close the Computer Management console. 2. If necessary, transfer data to the new disk. You can use disk imaging software to accomplish this.

REMOVE A MASS STORAGE DEVICE

1.Prepare to work inside the computer case. a.Set up ESD protective devices. b.Power down the computer and disconnect the power cord. c.Remove the case cover. 2.Disconnect the power supply and data cables. Try to pull the plug rather than the cable—hard drive (Molex) power connectors have special "shoulders" for this purpose. 3. Once the cables are removed from the storage device, undo the screws that hold the device to the case. Note: To remove the drive you may first need to unscrew the caddy. In most cases, you will need to remove the second side panel. 4.If the device does not then slide out backwards, try sliding it out forwards. You may have to remove the front panel of your PC. Note: Remember that SSDs might be installed via a PCIe adapter card or via an M.2 adapter slot, rather than by a SATA port.

Drive Bays and Caddys

A drive can be fitted using a caddy. You screw the drive into the caddy and then screw the caddy into the case. A caddy can also allow you to fit a drive of a different size to the bay. For example, you can fit a 2.5" drive in a 3.5" bay by using an adapter caddy. Some caddies use rails so that you can pull the drive out without having to open the case.

Blue Screen of Death (BSOD)

A failing hard disk and file corruption may cause a particularly severe read/write failure, resulting in system STOP errors (a crash screen).

Self-Monitoring Analysis and Reporting Technology (S.M.A.R.T.)

All drives now feature this which can pass status information and alerts back to monitoring software. This can provide advance warning that a drive is about to fail.

Dual-Drive configuration

Another option is for separate SSD and HDD units to be installed in a dual-drive configuration. In this case, the system chipset and storage drivers,based on Intel Smart Response Technology (SRT), make the caching decisions. Again, the user does not have control over the use of the SSD. Note: SRT can only use caches up to 64 GB (at the time of writing). If the SSD is larger, SRT can reserve part of the drive for caching and the remainder of the capacity is then available to the user and can be manipulated via the OS disk and file management tools.

Digital Rights Management (DRM) and region coding

Consumer DVDs feature copy protection mechanisms such as Digital Rights Management (DRM) and region coding. Region coding, if enforced, means that a disc can only be used on a player from the same region. -Region 0: No coding (playback is not restricted). -Region 1: Canada and the US. -Region 2: Europe, the Middle East, Japan, South Africa, and Egypt. -Region 3: SE Asia. -Region 4: South America, Australia, and New Zealand. -Region 5: Russia, parts of Africa, and parts of Asia. -Region 6: China. Like DVDs, consumer Blu-ray Discs (BD-ROMs) are likely to be DRM-protected and may be region coded: -Region A: America, Japan, and SE Asia. -Region B: EMEA, Africa, Australia, and New Zealand. -Region C: Russia and Central Asia (including China).

Dual Inline Memory Module (DIMMs)

DDR for desktops - DIMM - 184 pins with notches - DDR2 and DDR3 are both packaged in 240-pin DIMMs but are not compatible. - DDR4 288 pins, more power efficient @ 1.2 V

DDR2/DDR3/DDR4 SDRAM

DDR has been superseded by DDR2 (from 2003), DDR3 (from 2007), and DDR4 (from 2014) SDRAM. These increase bandwidth by multiplying the bus speed, as opposed to the speed at which the actual memory chips work. This produces scalable speed improvements. The drawback is increased latency, as data takes longer to access on each chip. Latency is offset by improving the memory circuitry.

DVD-R/DVD-RW

DVD±R supports dual layer and double-sided media, whereas DVD±RW supports double-sided media only. - start recording from the center and file out toward the outside edge

Constant LED activity

Disk thrashing can be a sign that there is not enough system RAM as data is continually moved between RAM and the pagefile.

RAM etc.

Note: When specifying high performance RAM you may want to compare the performance timings. These are quoted as a series of numbers in the form 5-5-5-15. Each number represents a different timing statistic. The lower the numbers, the better the performance. Each DDR standard has timing variants. For example, DDR3-1333G has 8-8-8-12 timing, whereas DDR3-1600G8 has 8-8-8-10 and DDR3-1600K has 11-11-11-13. More information on SDRAM standards can be obtained from jedec.org. Note: Clock speeds ending 33 or 66 are usually rounded down; technically they are 33⅓ and 66⅔. In the case of DDR2-667, the memory manufacturers just didn't like the look of "DDR2-666" so they rounded up.

Serial Presence Detect (SPD) ROM chip

Reports memory module characteristics to the system BIOS

Rotational Latency(HDD)

Sector location on the drive

DISK PERFORMANCE ISSUES

Slow disk performance is often a bottleneck for modern computer systems. In this case, the best solution may be to add more RAM rather than replace the disk or to upgrade the disk to an SSD or hybrid drive. -Disk defragmentation is also useful -Low disk capacity can also be a cause of slow performance. When a disk is 90% full,Windows warns the user via the notification area when disk space is critically low (below 200 MB). If the disk continues to be filled up, system performance will decline -Disk Cleanup program to free up space, but the user may have to take manual steps, such as moving or deleting files, uninstalling unnecessary applications, and so on.

How to set a DVD drive region in Device Manager

The DVD region supported by a PC DVD drive can be changed via Device Manager—though the firmware only permits a limited number of changes. (Screenshot used with permission from Microsoft.)

Memory Module

a printed circuit board that holds a group of memory chips that act as a single unit. Memory modules reside in slots on the motherboard, and they are removable and replaceable. Memory modules are defined by their design and by the number and type of chips they contain. -DIMM, SODIMM,

Blu-Ray Drives

also capable of CD and DVD playback and burning. Recordable (BD-R) and re-recordable (BD-RE) drives and discs are also available. BD-R is often available at the same speed as playback while BD-RE is usually half playback speed.

bootrec /fixmbr

attempt to repair MBR

Internal Transfer Rate (HDD)

data or disk transfer rate measure of how fast read/write operations are performed on the disk platters. A 15 K drive should support an internal transfer rate of up to about 180 MBps, while 7.2 K drives will be around 110 MBps

Invalid media type error message

disk has no valid file structure

Invalid Drive Specification error message

drive has an invalid partition structure

Power On Self-Test [POST]

firmware hardware check during boot

chkdsk/f

fixes file system errors but does not identify bad sectors

Disk Thrashing

is a problem that may occur when virtual memory is being used. As main memory fills up, then more and more pages need to be swapped in and out of virtual memory. This swapping leads to a very high rate of hard disk access.

RAM Types

notable RAM vendors include Kingston®, Crucial™ (Micron), Corsair, PNY, and Integral™.

buffer underrun

once the writing process starts, it cannot be paused. Therefore, if the OS does not supply data to the burner's buffer quickly enough, errors will be introduced into the disc's layout - most new writers ship with buffer underrun protection

Single-channel memory

one 64-bit bus between the CPU and RAM

BURN-proof technology

prevents discs being ruined by buffer under-run errors (where the software cannot supply the drive the data to write quickly enough).

mass storage devices

non-volatile data storage Mass storage devices use magnetic, optical, or solid state technology to store data.

Hardware RAID Solution

- A hardware RAID solution motherboard or plug-in controller card is responsible for creating the volume from an array of discs, independently from the OS -Hardware solutions are differentiated by their support for RAID levels. -Entry-level controllers support RAID 0 or RAID 1, -mid-level controllers support RAID 5 and RAID 10. - hardware RAID is often able to hot swap a damaged disk (replacing the disc without shutting down Windows) so the system operational all the time. -Hot swapping is a feature of high-end hardware RAID solutions and requires a compatible controller and disk units. -When the new disk is installed, the RAID controller transparently synchronizes it with the remaining disks in the set. -disadvantage = hardware RAID is more expensive than a software solution and may lock you into a single vendor solution. -Modern low cost RAID solutions may use the SATA interface -Server class machines often use Serial Attached SCSI (SAS) i The array is normally configured by launching the firmware configuration utility by pressing the appropriate key combination during startup. -Sometimes a RAID controller configuration tool is available from within the OS, too.

PATA/ATA standards

- ATAPI stands for ATA Packet Interface and is an extension to ATA to support CD/DVD drives and tape drives. - DMA (Direct Memory Access) mode refers to the way that data is transferred to and from system memory. - In the early days of the EIDE interface, BIOS versions severely restricted maximum drive capacity. Driver software in the OS now handles drive addressing. Logical Block Addressing (LBA) is a method of telling the drive how to address a particular place on the disk surface. 48-bit LBA supports drives up to a (theoretical) 144 Petabytes.

Write Once Read Many (WORM)

- CD-R is a type of this

Dynamic RAM (DRAM)

- DRAM stores each data bit as an electrical charge within a single bit cell. A bit cell consists of a capacitor to hold a charge (the cell represents 1 if there is a charge and 0 if there is not) and a transistor to read the contents of the capacitor. The electrical charge gradually dissipates, causing the memory cell to lose its information. In order to preserve the information, dynamic memory has to be refreshed periodically by accessing each bit cell at regular intervals. The refresh cycles slow down the operation of DRAM but it supports high densities (more MB per memory module) and is relatively low cost. Many types of DRAM have been developed and become obsolete.

Raid 1 (Mirroring)

- Mirroring requires two hard disks. The mirror disk is a duplicate of the data disk. Each write operation is duplicated on the second disk in the set = small performance overhead. - A read operation can use either disk, boosting performance somewhat. - This strategy is the simplest way of protecting a single disk against failure. -If one disk fails (degrading the array), the other takes over. There is little impact on performance during this time - the failed disk should be replaced as quickly as possible as there is no longer any redundancy. When the disk is replaced, it must be populated with data from the other disk (resynching). - Performance while rebuilding is reduced, though RAID 1 is better than other levels in that respect and the rebuilding process is generally shorter than parity-based RAID. -In terms of cost per gigabyte, disk mirroring is more expensive than other forms of fault tolerance because disk space utilization is only 50 percent. -the total volume size cannot exceed the available capacity of the physical disks. -disk mirroring has a lower entry cost because it requires only two disks and a relatively cheap RAID controller (or software RAID). -The availability of cheap, large HDDs makes the 50% overhead less of a drawback.

Optical Drives

- Optical drives include CD drives, DVD drives, and Blu-ray drives. - larger than hard disks (5.25" form factor). - internal unit installed to a 5.25" drive bay and connected to the motherboard via SATA data and power connectors. -external unit would be connected via USB (or possibly eSATA or Thunderbolt). External optical drives typically require their own power supply, provided via a supplied AC adapter. - CD drives are rated according to their data transfer speed. The original drives had a data transfer rate of 150 KBps. -drives have been available that offer multiples of the original rate; this would be around 52x for new models, offering transfer rates in excess of 7 MBps. Many optical drives also function as recordable/rewritable CD burners (or writers). -Such drives feature three speeds, always expressed as the Record/Rewrite/Read speed (for example, 24x/16x/52x). -important to ensure that a drive has BURN-proof technology

RAID 1+0 (RAID 10)

- RAID 0 is striping with no parity (that is, no fault tolerance is provided). This provides high throughput, but leaves the volume at risk. RAID 1 provides mirroring; the highest achievable disk fault tolerance. - RAID 1+0 (also called RAID 10) is a combination of both these configurations (nested RAID). - a logical striped volume is configured with two mirrored arrays. This configuration offers excellent fault tolerance as one disk in each mirror can fail and the array will still function. -at least four disks needed to create this configuration and there must be an even number of disks. Note that it carries the same 50% disk overhead that mirroring does.

RAID 5 (striping with distributed parity)

- Striping with distributed parity (RAID 5) writes error checking information across all the disks in the array. -data and parity information always on different disks. - If a single disk fails, information is spread across the other disks so the data can be reconstructed. -Stripe sets with parity offer the best performance for read operations. -when a disk has failed, the read performance is degraded by the need to recover the data using the parity information. Also, all normal write operations suffer reduced performance due to the parity calculation. - minimum of three drives but can be configured with more - more flexibility in determining the overall capacity of the array than is possible with RAID 1. -A "hard" maximum number of devices is set by the controller or OS support, but the number of drives used is more likely to be determined by practicalities such as cost and risk. -adding more disks increases the chance of failure. -The level of fault tolerance and available disk space is inverse. As you add disks to the set, fault tolerance decreases but usable disk space increases. -If you configure a RAID 5 set using 3 disks, a third of each disk is set aside for parity. If four are used, one quarter is reserved on each disk. Using a three 80 GB disk configuration, you would have a 160 GB usable volume. (basically 1 disc is always reserved) Note: If the disks are different sizes, the size used is that of the smallest disk. Extra disk space on larger drives is wasted.

Access Time (HDD)

RPM helps determine this. access time is the delay that occurs as the read/write head locates a particular track position (seek time) and sector location (rotational latency) on the drive. A high performance drive will have an access time below 3 ms; a typical drive might have an access time of around 6 ms.

Memory Compatibility Issues

- The DIMM format must match the motherboard (you cannot install DDR modules in DDR2 slots, for instance). - Different capacity modules can be installed (with the exception of most multi-channel configurations). Most vendors recommend installing the largest module in the lowest numbered slot. - Modules from different vendors can be mixed, though this may cause problems with multi-channel configurations. - For best performance, the modules should be the same speed as the motherboard. Different speeds can be mixed; that is, you can add modules that are faster or slower than the motherboard slots or mix modules of different speeds. The system will only operate at the best speed supported by all installed components (memory modules and controller), -For best performance and reliability, configure multi-channel systems with identical memory modules for each channel. - ECC memory cannot be mixed with non-parity memory and must be supported by the motherboard. Similarly, registered memory cannot be mixed with unbuffered modules and must be supported by the motherboard.

wmic /node:localhost diskdrive

- a S.M.A.R.T check that gets hard drive status

Disk Defragmentation

- contents of a disk are moved around to optimize disk access times. The components of a file (known as clusters) are placed adjacent on the disk surface (they are said to be contiguous). -Windows normally tries to run the defragmenter periodically as a scheduled task, but this process can be interrupted by -It may be necessary to run the tool manually during a "downtime" period.

Memory-Card Reader

- designed to fit in a front-facing 3.5" drive bay, though some can be fitted to a 5.25" bay. The reader then needs to be connected to a USB hub. - Most motherboards have at least one spare 9-pin USB header for making internal connections, or the reader may come with an expansion card - Alternatively, you may be able to run a USB converter cable from the reader to one of the external USB ports. Note: To support the fast speeds of modern card types, the reader must be connected to a USB 3 port. Another option is an external USB memory card reader.

xD card

- discontinued - used on Olympus cameras

DVD DS

- double sided DVD - Double-sided discs need to be turned over to play or record to the second side.

DVD DL

- dual layer dvd

Solid State Drives

- flash memory-based - less prone to damage - Read times are better because seek time and consequently the effect of file fragmentation is eliminated. - not as much data loss - Most drives still feature DRAM-based write cache to improve performance. In the event of a power failure, unwritten cache would be lost. However, the DRAM cache may be backed up by a battery to cover this eventuality. - drawback is that the 6 Gbps SATA interface can be a bottleneck to the best performing SSDs. Consequently, modern SSDs often use the PCI Express (PCIe) bus directly. A PCIe-based SSD can either be implemented as a regular PCIe adapter card or Add-in Card (AiC) or it can use the M.2 adapter interface. Note: SATA 3.2 defines SATA Express (SATAe) as a means of interfacing with a 2-lane PCI Express bus. It uses a different connector, but the port is backwards-compatible with "ordinary" SATA cabling. You might also come across the U.2 (or SFF-8369) interface. U.2 uses the same physical interface as SATA Express and is hot-swappable, but supports up to 4 PCIe lanes, like M.2. - HDDs outperform SSDs when they are serving large GB files Flash chips are also susceptible to their own type of degradation over the course of many write operations, so the drive firmware and operating system must use wear leveling routines to prevent any single storage location from being overused and optimize the life of the device.

Error Checking and Correcting (ECC) memory

- for systems that require a high level of reliability (workstations and servers) - ECC memory is enhanced parity circuitry that can detect internal data errors and make corrections. ECC will detect and correct single-bit errors and allow the system to continue functioning normally. It will also detect errors of 2, 3 or 4 bits but will not correct them; instead, it will generate an error message and halt the system. - ECC memory has an extra chip and a 72-bit data bus rather than 64-bit. The motherboard must support the use of ECC memory modules ECC memory cannot be mixed with non-ECC modules. - An ECC DIMM will have an odd number of memory chips, whereas non-parity DIMMs will have an even number of memory chips.

Small Outline DIMM (SODIMM)

- laptop DDR - DDR and DDR2 use 200-pin packages, but the key position for DDR2 is slightly different - DDR3 uses a 204-pin package -DDR4 is 260-pin. The memory is typically fitted into slots that pop-up at a 45º angle to allow the chips to be inserted or removed.

M.2

- not hot swappable or hot swappable - supplies power over the bus so there is no need for a power cable - can use up to 4 PCIe lanes - 42, 60, 80, 110mm lengths Note: Note that M.2 is a physical form factor and so you can obtain M.2 SSDs that use the SATA/AHCI bus. These will not perform as well as NVMe-based M.2 SSDs. On the motherboard, an M.2 socket may be able to support both types of drive or only one; check the documentation. The key position on the connector is different for SATA and NVMe models. Also note that M.2 can be used for wireless adapters too.

Pandonic DVD-RAM

- not widely supported by computer drives - optimized for multiple write operations - better for data storage

S.M.A.R.T (Self-Monitoring, Analysis, and Reporting Technology)

- self diagnostic program ran by windows to alert the OS is reliability is compromised wmic /node:localhost diskdrive is a command to perform a S.M.A.R.T check

CD Drive

- spindle motor (to spin the disc) - laser and lens (to read the disc) - tracking system to move the laser and lens assembly. The mechanism for inserting a CD is either tray or slot based. - Slot-loading mechanisms have rollers that grab the disc. Sometimes, these cannot handle non-standard disc sizes. -may feature audio play and volume controls and a headphone jack.

non-parity

- system memory for most desktops, meaning that it does not perform any error checking

DDRx RAM

- the increasing speed and architectural improvements of CPU technologies led to memory becoming a bottleneck to system performance. - Intel® and AMD developed a dual-channel memory architecture for DDRx RAM. - Dual-channel was originally used primarily on server-level hardware but is commonly being employed on desktop systems and laptops too.

Hard Disk Drive (HDD)

- up to 8TB - data is stored on several metal or glass platters that are coated with a magnetic substance. The top and bottom of each platter is accessed by its own read/ write head, moved by an actuator mechanism. - These heads do not touch the surface of the platters. The platters are mounted on a spindle and spun at high speed and the heads "float" above them at a distance of less than a millionth of an inch. - The disk unit is kept sealed to maintain a constant air pressure (important for keeping the drive heads at the correct distance from the platters) and to prevent the entry of dust. - Each side of each platter is divided into circular tracks and each track contains several sectors, each with a capacity of 512 bytes. This low-level formatting is also referred to as the drive geometry. There are two main formats for HDDs: 3.5" units=mainstream 2.5 " form factors=laptops and as portable external drives. There is also a 1." form factor but it is not widely used. 2.5" HDDs can also vary in height, with 15 mm, 9.5 mm, 7 mm, and 5 mm form factors available. - High performance drives are rated at 15,000 or 10,000 rpm; average performance is 7,200 or 5,400 rpm.

bootrec tool

- used at the boot command prompt to recover files if there are errors or a virus which is causing the PC not to boot into the OS

Non-Volatile Memory Host Controller Interface Specification (NVMHCI) or NVM Express (NVMe)

- used by PCIe based SSD's to communicate with the bus - logical interface

Advanced Host Controller Interface (AHCI)

- used by SATA to communicate with the bus

Blu-ray Discs (BDs)

- used to distribute large applications, such as video games. -required to cope with the demands of High Definition video recording and playback. HD requires more bandwidth and storage space because it uses a much higher resolution picture (1920x1080 compared to 720x480 [NTSC] or 720x576 [PAL]) and better quality audio (digital surround sound). -A Blu-ray Disc has shorter wavelength laser (a 405 nm blue laser) than DVDs -discs can be higher density, but more costly - 4.5 MBps = base speed and the - maximum theoretical rate is 16x (72 MBps). - 2x is the minimum required for movie playback. - A standard BD has a capacity of 25 GB per layer;

Serial Attached SCSI (SAS)

- very popular with servers (similar to SATA) supports up to 16000 devices -offers point-to-point links as opposed to shared bandwidth - no termination issues (unlike SCSI) - supports higher bandwidths (up to 12 GBPs)

Network Attached Storage (NAS).

- when a drive enclosure supports ethernet networking

Quad Layer BD (BD-XL)

-128GB but not currently recordable -BD-XL specification

CD-ROM

-700mb capacity which delivers most software applications -A CD is a layer of aluminum foil encased in plastic The foil layer contains a series of pits and spaces in-between (called lands) arranged in a spiral. The changes between pits and lands are used to encode each bit. - A standard CD is 120 mm in diameter and 1.2 mm thick. There are also 80 mm discs, which are playable in most CD-ROM drives. - Most CD players (except older equipment) can read CD-Rs Note: While the regular capacity of a CD is 700 MB, there are high capacity 800 MB (90 minute) and 860 MB (99 minute) discs that can be used with a CD writer that supports overburning. Note that overburning is more likely to produce disks with data or playback errors.

CD-R

-CD-Rs feature a layer of photosensitive dye instead of pits and lands -Recordable version - A special laser is used to transform the dye, mimicking the pits and lands of a normal CD, in a process called burning. -type of WORM media - Can only be written to once, however can have multiple data burned onto them if there is room

External Storage Devices

-External drives are packaged in a drive enclosure. The drive enclosure usually provides USB, Thunderbolt, and/or eSATAp ports. The enclosure also provides for an external power supply if needed -Some enclosures support Network Attached Storage (NAS). - -Advanced enclosures are designed to host multiple disk units, possibly configured in a RAID array to provide better data security.

GUIDELINES FOR TROUBLESHOOTING OPTICAL DRIVES

-Optical drives can generally go for a very long time between failures because drive reader does not touch the disc. -All reading/writing with recordable/re-writable media is done using lasers. -magnetic media drives such as floppy drives, where the read/write heads touch the disc are more likely to get dirty -dSpecial cleaning kits are available for cleaning optical drives if read/write problems are experienced. Most problems related to dirt, though, are caused by dirt on the disc itself. • Support for CD drives is built into Windows. If your CD drive is not able to read CDs at all, it is likely to be a hardware problem. • DVD-Video requires MPEG decoding hardware or software (codecs) to be installed for playback. This is supplied with Vista Home Premium and Ultimate editions and in each edition of Windows 7 except Starter and Home Basic. Windows 8 requires third-party software to be installed. Remember also that a DVD-ROM cannot be read from a CD-ROM drive. •There is currently no native support for Blu-ray in any version of Windows, but the drive should be bundled with the appropriate codecs and software.

Flash Memory Devices

-Solid State Drives, flash drives, memory cards, -flash memory =type of non-volatile Electrically Erasable Programmable Read-Only Memory (EEPROM), also referred to as NAND flash. -non-volatile because it does not need a power source to retain information. -capacity ranges from 512 MB to 256 GB.

Globally Unique ID (GUID) Partition Table (GPT)

-The boot information is not restricted to a single sector, but still serves the same basic purpose of identifying partitions and boot loaders. -GPT is associated with UEFI firmware, but can also be used by most legacy BIOS firmware if supported by the OS (32-bit Windows has problems booting from a combination of GPT and BIOS). -GPT is not subject to the restrictions on number and size of partitions that limit MBR; there are still limits, but not ones that are likely to be reached in practice. Note: GPT often uses a "protective" MBR to prevent disk tools from overwriting the GPT.

Installing Mass Storage Devices Considerations

Does the computer have existing internal storage devices? Do you need to plan for the addition of another controller for an additional device? You might need to purchase an additional SATA controller before you can add another SATA device. In addition, make sure that the computer has an available slot for the controller. Does the device need additional drivers installed? Make sure that you have the appropriate operating system device drivers to install the new storage device on the computer. If necessary, download the device drivers from the device manufacturer's website. Does the computer have an available power supply cable to supply power to the device? If not, you can purchase splitters to enable two (or more) devices to be connected to a single power connection, but be aware of power consumption. The number of connectors approximates the available power, so make sure that the storage device will not cause the computer to exceed the capacity of its power supply. Does the computer have an available drive bay for the storage device? Most hard drives require a 3.5-inch drive bay; most tape drives and optical drives require a 5.25-inch drive bay. If you want to install a hard drive in a 5.25-inch drive bay, you will need drive rails. Make sure you place the storage device where it will get good air flow to avoid overheating the device. Consider the placement of the drives inside the bays with the cable configurations. You may need to adjust the placement of the drives to match the order of cable connectors. Do you have the necessary data cables to connect the storage device to the controller? You will need a SATA data cable for each hard drive in the PC. Other types of storage devices might require different types of data cables. Does the placement of the device interrupt the air flow of the case? Make sure there is enough total air flow to handle whatever heat the new storage device will add to the computer.

Electrically Erasable Programmable Read-Only Memory (EEPROM)

Flash memory is a type of this

HDD Performance Factors

High performance drives are rated at 15,000 or 10,000 rpm; average performance is 7,200 or 5,400 rpm. RPM is one factor determining access time (measured in milliseconds), which is the delay that occurs as the read/write head locates a particular track position (seek time) and sector location (rotational latency) on the drive. A high performance drive will have an access time below 3 ms; a typical drive might have an access time of around 6 ms. internal transfer rateof a drive is a measure of how fast read/write operations are performed on the disk platters. A 15 K drive should support an internal transfer rate of up to about 180 MBps, while 7.2 K drives will be around 110 MBps. external transfer rate measures how fast data can be transferred to the CPU across the bus. Cache memory can help to sustain better transfer rates. A high performance disk may feature an 8 MB or better cache. The other crucial factor that impacts HDD performance is reliability which is rated by various statistics, including Early-life Failure Rate, Mean Time Between Failure (MTBF), which is the number of hours that a device should operate (under optimum conditions) before a critical incident can be expected, and life expectancy, which is the duration for which the device can be expected to remain reliable. All drives now feature Self-Monitoring Analysis and Reporting Technology (S.M.A.R.T.) to pass status information and alerts back to monitoring software. This can provide advance warning that a drive is about to fail. -Some of the major hard drive vendors include Seagate, Western Digital, Maxtor, Hitachi, Fujitsu, Toshiba, and Samsung.

BD R

Recordable Blueray

TROUBLESHOOTING RAID ISSUES

If Windows does not detect a RAID array during setup or at boot time: •Check that the drivers for the RAID controller are installed and use the RAID configuration utility to verify its status. Boot message indicating a problem with the RAID volume—press Ctrl+C to start the utility and troubleshoot. •If you cannot access the configuration utility, then the controller itself could have failed. If RAID stops working: •One of the purposes of using RAID (or at least RAID 1/5/10) is that it is much less likely than a simple disk system to just "stop working." If one of the underlying disks fails, the volume will be listed as "degraded," but the data on the volume will still be accessible. Note: RAID 0 has no redundancy, so if one of the disks fails, it will stop working. In this scenario, you had better hope that you have a recent data backup. •The precise process for managing a disk failure with an array will be dependent on the vendor that supplied the array and the configuration being supported. All array controllers will be capable of generating an event to the OS system log and perhaps of generating an alert message for the administrator. RAID errors using the configuration utility - this volume is missing one of its disks. •Most desktop-level RAID solutions can tolerate the loss of only one disk, so it should be replaced as soon as possible. If the array supports hot swapping, then the new disk can simply be inserted into the chassis of the computer or disk chassis. Once this is done, the array can be rebuilt using the RAID configuration utility (if a hardware RAID controller is used) or Disk Management (if you are using dynamic disks to implement "software" RAID). Note that the rebuilding process is likely to severely affect performance as the controller is likely to be writing multiple gigabytes of data to the new disk. Note: When hot swapping a faulty disk out, take extreme caution not to remove a healthy disk from the array as making a mistake could cause the array to fail, depending on the configuration. Disk failure is normally indicated by a red LED. Always make a backup beforehand. •If a volume is not available, either more than the tolerated number of disks has failed or the controller has failed. If the boot volume is affected, then the operating system will not start. If too many disks have failed, you will have to turn to the latest backup or try to use file recovery solutions. If the issue is controller failure, then data on the volume should be recoverable, though there may be file corruption if a write operation was interrupted by the failure. Either install a new controller or import the disks into another system.

Boot Failure

If the hard drive is not detected at boot (or if a second hard drive is not shown under Windows), -first check that it is powering up. Drive activity is usually indicated by an LED on system case, if this is inactive, check that power connector is attached to the drive -If the PC has no LEDs, or you suspect that they may be faulty, it is usually possible to hear the hard drive spinning up. Once you have determined that the drive is powering up, try the following: --If the system is not booting correctly from the hard drive, check that the boot sequence is set correctly in the PC firmware system setup program and that there are no removable disks in floppy or optical drives. --Check that data cables are not damaged and that they are correctly connected --If the drives are connected to a motherboard port, check that it has not been disabled by a jumper or via system setup. Once you have determined that the drive configuration is correct, try the following. If a boot hard drive is detected by the firmware hardware check (Power On Self-Test [POST]) but not by Windows (for example, if you get an error such as "OS not found"), there is probably a problem with the file system. Boot into the recovery environment using the Windows setup disc and enter C: at the command prompt. If this produces the error message Invalid media type, the disk has no valid file system structure on it. This may be caused by surface errors or by a virus. You may be able to recover from this by running the bootrec tool at a boot command prompt or by reformatting the disk (at the expense of any data, of course). If you enter C: at the command prompt and you see the error message Invalid drive specification, the drive may have an invalid partition structure. You can check the drive's partition structure with diskpart.

Synchronous DRAM (SDRAM)

In the mid-1990s, variants of SDRAM were used for system memory. SDRAM is so-called because it is synchronized to the system clock. It has a 64-bit data bus. Consequently, if the bus is running at 66 MHz, the bandwidth available to an SDRAM memory controller is 66.6*64 or 4266 megabits per second. Dividing by 8 gives the bandwidth in megabytes per second (533 MBps).

SCSI Standards

InterfaceProtocol Standard Bandwidth Buswidth MaxCableLength SCSI-I SCSI-I 5MBps 8bits SE:6,LVD:NA,HVD:25 Fast SCSI SCSI-2 10MBps 8bits SE:6,LVD:NA,HVD:25 Fast-Wide SCSI SCSI-2 20MBps 16bits SE:3,LVD:NA,HVD:25 Ultra SCSI SCSI-3 20MBps 8bits SE:1.5,LVD:NA,HVD:25 Ultra-Wide SCSI SCSI-3 40MBps 16bits SE:NA,LVD:NA,HVD:25 Ultra2 SCSI SCSI-3 40MBps 8bits SE:NA,LVD:12,HVD:25 Ultra2 Wide SCSI SCSI-3 80MBps 16bits SE:NA,LVD:12,HVD:25 Ultra3 SCSI (Ultra160 SCSI) 3 160MBps 16bits SE:NA,LVD:12,HVD:NA Ultra320 SCSI SCSI-3 320MBps 16bits SE:NALVD:12,HVD:NA

Boot Block Repair

One of the unwelcome actions that malware can perform is to damage the boot information on the hard drive. There are two ways of formatting the boot information: MBR and GPT. Whether the disk is using an MBR or GPT partitioning scheme, damage to these records results in boot errors such as "OS not found" or "Invalid drive specification." If this problem has been caused by a virus (it can also occur due to disk corruption or installing operating systems with conflicting boot loaders in multiboot configurations), the best way to resolve it is to use the boot disk option in your antivirus software. This will include a basic antivirus scanner that may detect the virus that caused the problem in the first place. If you don't have the option of using a recovery disk created by the antivirus software, you can try to use the repair options that come with the Windows product disk. Be aware that these may not work completely reliably if the system is still infected with a virus. 1.Boot from the product disk and select the Repair option. 2.First, try to use the Startup Repair option. If this does not work, select the Command Prompt option. •Enter bootrec /fixmbr to attempt repair of the MBR. •Enter bootrec /fixboot to attempt repair of the boot sector. •Enter bootrec /rebuildbcd to add missing Windows installations to the Boot Configuration Database (BCD). 3.Restart the PC. Note: These tools may not be suitable for use with multiboot configurations if one of the other OSes has created a non-standard partition table.

COMMON RAID CONFIGURATION ISSUES

RAID not found. RAID stops working.

Remove/Install DIMMs

REMOVE 1. Open the system case, using ESD precautions. 2. Locate the RAM slot that contains the DIMM you want to remove. 3. Release the retaining clips that hold the DIMM in place. 4. Use your fingers to grasp the DIMM by its edges and remove it completely from the slot. Avoid touching the chips. INSTALL 1. Open the system case, using ESD precautions. 2. Locate a spare memory socket. Most memory sockets are numbered on the motherboard. This numbering may start at 0 or 1. Some motherboards allow these slots to be filled in any order, but most require that you fill the slots from the lowest numbered slot upwards. Refer to the motherboard documentation for any specific requirements. 3. Open the retaining clips for the selected RAM slot. 4. Line up the memory card. Verify that the notches in the memory card are aligned correctly with the memory socket before you attempt insertion. 5. Insert the memory card. DIMMs are pushed straight down into the socket. 6. Reboot the PC and watch the RAM count during startup to verify that the memory has been recognized. Note:. Note that modern computers are likely to use fast boot modes and will not display diagnostic information such as the RAM count at startup. 7. In Windows, you can check the installed RAM by looking at the System Control Panel properties or the System Information app.

INSTALL A MASS STORAGE DEVICE

To install a mass storage device: 1. Prepare to work inside the computer case. a.Set up ESD protective devices. b.Power down the computer and disconnect the power cord. c.Remove the case cover. 2. Locate an available drive bay, power connector, port, and interface connector. • If you are adding a SATA drive, locate a SATA port on the motherboard or on a SATA host adapter card; then locate an available drive bay, power connector, and the SATA interface connector on the system board or SATA host adapter. Note: If your power supply does not have any SATA power connectors, you will need an adapter to connect a Molex power connector to these. If the drive has a legacy Molex power connector, you should only use one of the connectors (do not plug a power cable into both). •If you are adding an EIDE drive, locate an available drive bay, the PATA data connection on the PATA data cable, and a power connector. •If you are adding a SCSI drive, locate an available drive bay, the SCSI data connection on the SCSI data cable, and a power connector. 3.Address the necessary configuration issues. •For a SATA drive, there are no device settings to configure, but you should try to install the boot drive into the lowest numbered port (SATA0). •For an EIDE drive, set the jumpers for Cable Select, master, or slave, as appropriate to your needs. There is usually a sticker on the top of the drive that specifies the jumper settings for each of these functions. If there is not a sticker, then the documentation for the drive will include this information. •If the drive is the first drive on the channel, it should be configured as Cable Select or master. •IFthe drive is the second drive on the channel, it should be configured as Cable Select or slave. •If Cable Select is not available on your system, you should use the slave setting. •For a SCSI drive, configure SCSI identification and termination. 4.Connect the data and power cables. a.Attach the drive interface and power cables to the drive. b.Attach the drive interface cable to the appropriate interface connector. c.Attach the power cable to the power supply. 5.Insert the drive into a drive bay. a. If necessary, attach rails to the drive to fit in the drive bay. b.Slide the drive into the drive bay. c.Secure the drive by using the supplied mounting screws. 6.Restart the system. 7.If necessary, access system firmware setup to enable and configure the drive. •Check that the device has been recognized by the computer's system firmware. If the drive is not listed in the startup configuration pages, enter system setup and verify that the drive's host adapter is enabled. •For an SSD, you should also check that the port is using the appropriate mode (ATA compatibility mode, AHCI, or NVMe). You might also want to configure the drive as a boot device. Note: To boot from an NVMe SSD, the system firmware must be based on UEFI, not a legacy BIOS.

DVD+R/DVD+RW.

VD±R supports dual layer and double-sided media, whereas DVD±RW supports double-sided media only. -More compatible with devices than -R - start recording at the outside edge filling toward the center

System Memory

Volatile, RAM - necessary because it is much faster than accessing data in a mass storage system, such as a hard disk - Non-volatile memory does not require a constant power source to store data. Examples include read-only memory (ROM) and flash memory. - CPU, cache, and RAM are fast but volatile; mass storage and removable storage devices provide slower but permanent data retrieval If there is not enough system RAM, the memory space can be extended by using disk space (virtual memory), but as noted previously, accessing the disk is very slow compared to accessing RAM.

Seek Time (HDD)

When a hard locates a particular track position

Read/Write Failure

When you are trying to open or save a file, an error message such as "Cannot read from the source disk" is displayed.

Bad Sectors

When you run the chkdsk /r program it can test the surface of the hard disk. If more bad sectors are located each time the test is run, it is a sure sign that the disk is about to fail. Note: Use the Check Disk utility regularly to check that the drive is in good condition. chkdsk /f will fix file system errors but will not identify bad sectors.

Small Computer Systems Interface (SCSI)

is another parallel bus. One SCSI Host Bus Adapter (HBA) can control multiple devices, attached by internal ribbon cables or external SCSI cables. The SCSI standard also defines a command language that allows the host adapter to identify which devices are connected to the bus and how they are accessed. SCSI was used to connect peripherals of different types but is now only associated with the connection of storage devices. As with IDE, you will not find SCSI on new systems, but should know how to configure it in case you encounter any legacy systems still depending on it. A SCSI port is denoted by the following symbol: The main SCSI standards are described in this table. - Given the number of different versions of the standard, SCSI configuration is relatively complex. SCSI devices were typically used on server-class hardware rather than on desktop PCs. • Host adapter—the SCSI host adapter must be installed and recognized by the system for devices to be detected. A third-party driver might have to be installed for the host adapter to be recognized. • Bus width—SCSI originally supported 8 devices (the host adapter counts as a device). Wide SCSI supports up to 16 devices. • Signaling—SCSI specifies three signaling methods. Most buses and devices use Low Voltage Differential (LVD). Single Ended (SE) devices can be added to an LVD bus, but it reduces the performance of the whole bus. H(igh)VD is incompatible with the other two and must not be mixed. • Termination—a SCSI bus must be terminated at both ends, usually by enabling termination on the first and last devices in the chain. Termination may either be enabled internally on the device by setting a switch or by physically connecting a terminator pack to a device or the host adapter. Note: There are passive and active terminators. Passive terminators are generally used with older devices (pre-Ultra SCSI). When installing a terminator pack, the terminator must match the signaling type (SE, LVD, HVD, or SE/LVD). Termination is also made more complex if there is a mix of narrow (8-bit) and wide (16-bit) devices on the bus. • ID—each SCSI device must be allocated a unique ID, from 0 to 7 (or 15 for wide SCSI). IDs may be allocated automatically or by setting a jumper or click-wheel on the device itself. The order of SCSI ID priorities (from highest to lowest) is 7 through to 0 then 15 through to 8. Note: The host adapter is usually set to 7 or 15. A bootable hard disk is usually allocated ID 0. There were numerous SCSI connectors. Some of the most common were: • HD68—68-pin connectors used for internal and external ports. 68-pin adapters support Wide SCSI. • Single Connector Attachment (SCA)—an 80-pin connector that incorporates both a power connector and configuration wires, allowing for hot swappable drives.

Parallel Advanced Technology Attachment (PATA)

legacy mass storage interface The interface was (and still is) also referred to as IDE (Integrated Drive Electronics) or EIDE (Extended IDE). As the name suggests, an EIDE bus uses parallel data transfers, meaning 16 bits is transferred for each clock tick. A motherboard supporting PATA may come with one or two host adapters or channels, called IDE1 and IDE2 or primary (PRI IDE) and secondary (SEC IDE). A single PATA channel is now more typical if the motherboard also supports SATA. Each PATA channel supports two devices, 0 and 1, though they are usually labeled master and slave. - A PATA drive features a 40-pin port but typically uses 80-wire shielded cables, which are required for UDMA4 or better transfer modes. -up to 46 cm (18") long. Each cable typically has three connectors, one for the motherboard and one for each device. Most cables are "Cable Select," allowing the master and slave device to be identified by the position of the connector on the cable. - Pin 1 on the cable must be oriented with pin 1 on the connector. On the cable, pin 1 is identified with a red stripe. The connectors are also keyed .

External Transfer Rate (HDD) aka Transfer Rate

measures how fast data can be transferred to the CPU across the bus. Cache memory can help to sustain better transfer rates. A high performance disk may feature an 8 MB or better cache.

Double Data Rate SDRAM (DDR SDRAM)

updated type of SDRAM where data is transferred twice in one cycle There are four DDR standards, matching different system clock speeds. - SDRAM is referred to by the bus clock speed (PC100, PC133, and so forth). DDR chips are labeled using the maximum theoretical bandwidth (PC1600, PC2100, and so on) largely for marketing reasons. For example, consider DDR-200 PC-1600 memory: • The internal memory clock speed and I/O bus speed are both 100 MHz. • The data rate is double this as there are two operations per clock "tick." This is expressed in units called MegaTransfers per Second (200 MT/s). This gives the DDR-200 designation. • The peak transfer rate is 1600 MBps (200 MT/s x 8 bytes per transfer). This gives the "PC-1600" designation. 1600 MBps is equivalent to 1.6 GBps. Note that the peak transfer rate does not represent "real world" performance; it is a maximum theoretical rate.

Logical Volume Manager (LVM)

used by LINUX to implement RAID via software

chkdsk

verifies integrity of formatted disc

Early-life Failure Rate, Mean Time Between Failure (MTBF)

which is the number of hours that a device should operate (under optimum conditions) before a critical incident can be expected

DDR3-1600/PC312800

works at 200 MHz and the bus at 800 MHz, which with the double data rate gives 1600 MT/s and nominal transfer rate of 12.8 GBps.

DDR4-1600/PC4-12800

works at 200 MHz and the bus at 800 MHz, which with the double data rate gives 1600 MT/s and nominal transfer rate of 12.8 GBps. The only advantage over DDR3-1600 is the lower voltage, reducing power consumption.

DDR2-1066/PC28500

works at 266 MHz and the bus at 533 MHz, which with the double data rate gives 1066 MT/s and nominal transfer rate of 8.533 GBps. This is the best available DDR2 standard.

DDR4-2400/PC4-19200

works at 300 MHz and the bus at 1200 MHz, which with the double data rate gives 2400 MT/s and nominal transfer rate of 19.2 GBps, exceeding anything available for DDR3.

TROUBLESHOOTING CD/DVD/BD WRITING

•Where Windows does not support a particular recordable or rewritable format directly, third-party software is required. • Some writable media are not made well, so errors during CD or DVD are common. Check that you are using the write speed recommended for the brand of discussed. If the error is persistent, however, it is not due to the media. •Most problems are connected to buffer underruns. On older devices, once the writing process starts, it cannot be paused. Therefore, if the OS does not supply data to the burner's buffer quickly enough, errors will be introduced into the disc's layout. The following solutions can usually be applied: •Try burning discs at a lower write speed. •Copy source files to the local hard disk (rather than removable or network drives). •Do not use other applications when burning a disc. •The latest CD and DVD writers usually ship with buffer underrun protection.