A+ chapter 6

USB flash memory

Also referred to as a memory stick, pen drive, thumb drive, or jump drive, is a solid state memory card enclosed in a case with an integrated USB interface. They are small in size, about the size of your thumb, thus the nickname "thumb drive."

RAID 5

Uses disk striping across at least three drives and includes parity data. If one of the drives in the array fails, the data that was stored on the failed drive can be recreated from the parity data on the remaining drives. RAID 5 has the read performance increase you'd see with RAID 0, plus it includes fault tolerance without using as much disk space as RAID 1.

Secure Digital (SD) Card

is a solid state memory card developed by the SD Card Association in 1999. SD cards come in three different sizes: the original (32.0 x 24.0 mm), mini-SD (21.5 x 20.0 mm) , and micro-SD (11.0 x 15.0 mm) .

SATA and IDE connections

SATA and IDE interfaces are easy to distinguish from one another. SATA cables are long and thin, with 7 wires. Older IDE devices used on legacy systems use use wide, ribbon-like 40-wire cables. The SATA connector has 7 pins and the housing is molded into an L-shape. SATA connectors can be straight, right-angled, or left angled.

SCSI connections

SCSI is an interface protocol used to connect storage devices and other peripherals. it is compatible with a wide variety of physical cables and connection types, and generally supports a larger number of devices on a single controller than ATA.

Magnetic HD/SSD comparison

SSDs have many advantages over hard drives. Since they have no moving parts, they're silent, don't suffer mechanical wear during operation, and are less susceptible to damage due to shock or magnets. They're also much faster, especially when it comes to random access of small amounts of data. Replacing a system HDD with an SSD will typically result in much faster boot times and increased system performance, and disk fragmentation won't really affect performance. Finally, they're available in much smaller form factors. A "full size" SSD is 2.5", and M.2 drives are even smaller.

Drive connections

Serial AT Attachment (SATA) connections are most common for modern hard drives on newer computers. Integrated Drive Electronics (IDE) connections are most common on older computers. Small Computer System Interface (SCSI) connections might be found in high end servers, specialized workstations, and older Apple hardware.

Flash drives and memory cards

Solid state storage technology comes in smaller forms such as USB flash drives and flash memory cards, used to store data on many mobile devices and digital cameras. These storage devices are removable and allow you to easily transfer their contents from one device to another.

RAID 0

Takes the contents of files and spread them in roughly even parts across all drives in the RAID array. Also known as disk striping, RAID 0 allows the CPU to read and write simultaneously on different drives, improving performance. It works with two or more disks, and the total space is equal to the sum of all drives in the array, but it does not include any fault tolerance

Hard drives are available in multiple form factors:

3.5" hard drives are most commonly used in desktop and server systems. 2.5" hard drives are most commonly used in laptop computers. 1.8" hard drives were once popular for small laptops and portable media devices, but cheap flash memory means you'll only find them in older devices.

Symptoms of a hard drive problem during use

1) Bad sectors: As a hard disk ages or if the hard drive platters have sustained physical damage, individual sectors will eventually fail. If system files reside in a bad sector, it can cause a Microsoft Blue Screen of Death (BSOD) or other operating system crash screen. 2) S.M.A.R.T. errors: Self-Monitoring, Analysis and Reporting Technology monitors attributes of your hard drive that indicate mechanical wear and degradation of storage surfaces, and reports when those attributes pass set threshold values. Many manufacturers include S.M.A.R.T. with their magnetic and solid state hard drives. 3) Slow performance: Constant read-write noise, a buzzing fan, and freezing are all symptoms of a slow hard drive. Things to try to resolve your performance issue: Run CHKDSK to scan for bad sectors on the hard disk, verify file system integrity, and attempt to fix any logical file system errors.

RAID failures

1) Drive failure - The hard drives in a RAID array have more simultaneous data reads and writes than a typical hard drive. 2) Controller failure - Most RAID implementations use a single RAID controller. If the controller fails, the entire RAID array fails. 3) Power issues - Problems with the power signal, such as surges or dirty power, can cause problems with the controller or one or more hard disks in your RAID array. 4) Software issues - For example, a virus or corrupt files. 5) RAID rebuild stress - When you lose a RAID drive, you replace the drive and rebuild its data from the partity information on the other drives.

Tape Drive

A drive that reads and writes data onto a magnetic tape, which is housed in a protective casing called a cassette or cartridge

Hot swapping

A hot swap occurs when you replace a hard drive, optical drive, or other component with a similar component while the computer or device remains in operation.

Hybrid drives

A hybrid drive is a magnetic hard drive with flash memory chips added to it. The flash memory chips act as a buffer for operating system and application files, allowing the system to boot up and start applications faster. T

RAID 10

A nested RAID level, also referred to as RAID 1+0. Nested RAID levels combine RAID 0 (data striping) with other RAID techniques. RAID 10 combines RAID 1 (mirroring) with RAID 0 (disk striping), making it a stripe of mirrors. RAID 10 requires four hard drives - two hard drives for the disk mirror and then two more disks to stripe the mirrored disks.

SCSI

A set of standards for physically connecting and transferring data between computers and peripheral devices.

Optical disc capacities

CD standard 650MB CD high-density 700MB DVD single-layer, single-sided 4.7GB DVD single-layer, double-sided 9.4GB DVD dual-layer, single-sided 8.5GB DVD dual-layer, double-sided 17GB Blu-ray (pre-BD-XL) 25GB per layer Blu-ray BD-XL triple-layer 100GB Blu-ray BD-XL quadruple-layer 128GB

Symptoms of a hard drive problem during POST

Hard drive not found Fixed disk error Invalid boot disk Inaccessible boot device Operating system not found A 1700s or 10400s numeric error code

Compact Flash

Is a solid state memory card standard developed by SanDisk in 1994. CF cards are larger than other memory card types - 42.8 x 36.4 mm, and either 3.3 mm or 5.0 mm thick. The original CompactFlash cards use a parallel ATA (PATA) connection interface.

There are two types of disk drives

Magnetic Solid State

Magnetic hard drives

Magnetic hard drives contain one or more round aluminum or glass platters which are coated with several layers of various materials.

Optical drive types

Optical drives use a laser to read information from, or write information onto, a flat circular disc. There are three types of optical drives available, and each comes in internal and external drive versions for both PC and laptop computers.

Advantages of tape drives and magnetic tape include

Reduced energy costs - Tape drives use less power and generate less heat than hard drives. Reliability - Magnetic tape is very stable and has a low error rate. High capacity - Tapes have a very high data capacity per square inch. For example, a single LTO tape cartridge can store up to 6.25TB of data. Low cost per GB - At an average of $.01/GB, the cost of data storage on tape is lower than other forms of data storage.

Optical drive issues

Read and write errors. Drive not recognized by the operating system. Drive does not eject a disc using either software eject or the eject button on the drive itself.

RAID

Redundant array of independent disks (RAID) is a data storage technology where you combine multiple hard drives into a single logical unit to add fault tolerance (also referred to as data redundancy) and improve performance. With RAID, two or more hard drives are configured into an array. Data is saved across the array. How the data is saved across the array depends on the RAID level configured.

RAID 6

Similar to RAID 5, except with at least four drives, and two parity disks. RAID 6 has the benefits of RAID 5, but with much stronger fault tolerance.

Hard drive issues

The power-on self-test (POST) Normal computer use

RAID 1

Writes identical data to two or more hard drives, also known as disk mirroring. You need at least 2 hard drives to configure a RAID 1 array. Read performance is improved slightly due to the fact that any free drive in the array can provide the CPU with the data it requests. RAID 1's main benefit is its fault tolerance. If one drive in the array fails, all the data is available on at least one other drive.

Solid state drives

a storage device that typically uses flash memory to store data, instructions, and information. Solid state drives (SSDs) store data on a series of non-volatile flash memory chips. Permanently installed on the motherboard. This type of memory is referred to as embedded multimedia card (eMMC). Installed on a PCIe card and plugged into a motherboard expansion slot