Chapter 5 Data Storage technology Questions

Describe serial, random, and parallel access. What types of storage devices use each method?

Serial access reads or writes data units in sequential order. Magnetic tape is the only widely used form of serial access storage. Random access can "jump" directly between two noncontinuous data units. All primary storage and disk storage devices use random access. Parallel access reads or writes portions of a data item in parallel on separate storage devices or media. RAM can be considered a parallel access device.

Why should you defragment magnetic disk drives? Why should you avoid defragmenting SSDs?

The defragmenter will search your hard drive partition and move data from one location to another location, so that the files stored there are one contiguous piece, instead of being spread throughout multiple locations on the hard drive's partition. This allows the programs and data on the magnetic disk drives to run more efficiently and quickly as the operating system does not have to read from multiple locations. SSDs doesn't take any extra time to read from different parts of the drive. So, defragmentation won't offer any performance increases Thus defragmenting SSD's is not a good idea.

Describe the processes of reading from and writing to a phase-change optical disc. How does the performance and areal density of these discs compare with magnetic disks?

A phase-change optical disc is coated with a material that's amorphous or crystalline. A bit area in the amorphous state is changed to a crystalline state y heating it to a certain temperature with a laser. A bit area in the crystalline state is changed to the amorphous state by heating it to the material's melting point. Phase-change optical discs have slower access time than magnetic disks because more time is required to heat a bit with a laser than to alter its magnetic polarity.

__________ is typically stated in milliseconds for secondary storage devices and nanoseconds for primary storage devices.

Access Time

The __________ of a magnetic or optical storage medium is the ratio of bits stored to a unit of the medium's surface area.

Areal Density

Which factors do magnetic storage device manufacturers balance to ensure high capacity and performance at reasonable cost and reliability?

Areal density: Manufacturers balance the areal density of the media coating with its coercivity to ensure high capacity and performance while reducing volatility and maintaining dependability. Spin rate: Manufacturers balance spin rate with device life. Faster spin speeds increase performance by reducing rotational delay, but they also accelerate the wear and failure of mechanical components such as bearings. Cost: Manufacturers balance the cost of materials, manufacturing, and distribution with the desired capacity and performance. Reliability: Manufacturers balance the reliability of the device with its capacity and performance by ensuring that the device can withstand various environmental conditions.

Why is the areal density of optical discs higher than the areal density of magnetic disks? What factors limit this areal density?

Because higher density on optical disk is achieved by tightly focused lasers that can access a very small storage space. Magnetic disks have small magnetic fields which cannot be focused on small areas without overwriting the surround bits.

The data transfer rate of a magnetic or optical disk drive can be calculated by dividing 1 by its access time and multiplying the result by the __________ size.

Block

In what way(s) is/are SSDs an improvement over magnetic disk drives? In what way(s) isn't/ aren't they an improvement over magnetic disk drives?

By avoiding all mechanical delays in accessing storage locations, SSDs yield a significant performance improvement compared to magnetic disk drives. However, their lifetime, as measured in write cycles, is significantly less than magnetic disk drives. Also, their cost per unit of storage is generally higher than for magnetic disk drives

List and briefly describe the standards for recordable and rewritable CDs and DVDs. Are any of the standards clearly superior to their competitors?

CD Standards CD-R (Compact Disc-Recordable): Allows you to write data once and read many times. It's good for archiving files but can't be erased or rewritten. CD-RW (Compact Disc-ReWritable): Enables you to write and rewrite data multiple times. Useful for dynamic data storage, but the rewritable nature means it's less durable for long-term storage. DVD Standards DVD-R and DVD+R: Similar to CD-R, these are recordable DVD formats where data can be written once. The "+" and "-" standards are similar, but the "+" version has some technical advantages, like better error handling. DVD-RW and DVD+RW: These are rewritable DVD standards. Again, similar to the CD-RW, but with higher storage capacity. Like the recordable versions, the "+" version has some minor technical advantages. DVD-RAM: This is a DVD standard that acts more like a removable hard drive, allowing for more random-access writing. It's highly reliable but not as widely supported. Are any standards superior? CDs: In th

__________, __________, and __________ are storage formats originally designed for music or video recording that have been applied to computer data storage

CD-DA, DVD, BD

Three standard optical storage media that are written only during manufacture are called __________ , __________ , __________ and __________ . .

CD-ROM DVD ROM BD

Describe current and emerging nonvolatile RAM technologies. What potential advantages do the emerging technologies offer compared with current flash RAM technology?

Current Nonvolatile RAM Technologies Flash RAM: This is your good ol' standard, commonly used in USB drives and SSDs. It's nonvolatile but has limitations like slower write speeds and a finite number of write/erase cycles. Ferroelectric RAM (FeRAM): Faster than Flash and also nonvolatile. However, it has limited storage capacity and is more expensive to produce. Magnetoresistive RAM (MRAM): Uses magnetic states to store data. It's fast and durable but currently expensive to produce. Emerging Nonvolatile RAM Technologies Phase-Change Memory (PCM): Uses heat to change the state of a material to store bits. It has the potential for high speed and high density but is still relatively expensive. Resistive RAM (ReRAM): Utilizes the resistance properties of materials to store data. It offers high speed and density and has the potential for lower power consumption. Spin-Transfer Torque MRAM (STT-MRAM): A variation of MRAM that uses less power and has the potential for higher density.

Modern desktop and laptop computers generally use memory packaged on small standardized circuit boards called __________. .

DIMMs

__________ ,__________ , __________ , and __________ are competing standards for rewritable DVD discs.

DVD-RW, DVD+RW, DVD-ROM, and BD

The __________ rate is the speed at which data can be moved to or from a storage device over a communication channel.

Data transfer

Average access time can usually be improved by __________ files stored on a magnetic disk drive.

Defragmenting

Describe the factors that contribute to a disk drive's average access time. Which of these factors is improved if the spin rate is increased? Which is improved if areal density is increased?

Disk average access time is a combination of rotational delay, track-to-track seek time (head movement), and head-to-head switching time. Rotational delay is reduced if spin rate is increased. If areal density is increased, TTT seek time is improved because tracks are narrower and packed together more tightly (more tracks per same unit of distance traveled by the read/write head).

How is data stored and retrieved on a magnetic mass storage device?

Exploits a duality: Electrical current generates a magnetic field, and a magnetic field can generate electricity.SO a MAGNETIC STORAGE DEVICE converts electrical signals into magnetic charges, captures the magnetic charge on a storage medium (to write to storage), and later regenerates an electrical current from the stored magnetic image (for retrieval) pp 170-71

__________ and __________ are promising new technologies for implementing NVM that promise significant increases in longevity.

MRAM, Polymer Memory

The __________ of a magnetic disk drive generates or responds to a magnetic field.

Read/Write head/s

Dynamic RAM requires frequent __________ to maintain its data content.

Refresh Cycles

A(n) __________ mimics the behavior and physical size of a magnetic disk drive but has no moving parts.

Solid State Drive (SSD)

What are the differences between static and dynamic RAM?

Static: Made with Flip Flops Dynamic: Made with Capacitors

What improvements are offered by synchronous DRAM compared with ordinary DRAM?

Synchronous DRAM (SDRAM) is a read-ahead RAM that uses the same clock pulse as the system bus. (P 167) Compared to ordinary DRAM, SDRAM activates the circuitry for location n+1 during or immediately after the access of location n to speed things up.

What factors limit the speed of an electrically based processing device?

The size and the operating temperature of the device

A(n) __________ is a series of sectors stored along one concentric circle on a platter.

Tracks

The contents of most forms of RAM are __________ , making them unsuitable for long-term data storage.

Volatile

In a magnetic or optical disk drive, a read/write head is mounted on the end of a(n) __________.

access arm

For most disk drives, the unit of data access and transfer is a(n) __________ or __________ .

block, sector

Software programs stored permanently in ROM are called __________ .

firmware

The three components that are summed to calculate average access time for a disk drive are __________ , __________ , and __________ .

head-to-head switching time, track-to-track seek time, rotational delay

Why isn't flash RAM commonly used to implement primary storage?

it's much slower than DRAM

Data stored on magnetic media for long periods of time might be lost because of __________ and __________.

magnetic leakage, magnetic decay

__________ is a flash RAM technology that provides higher capacity than traditional 2D/planar flash RAM technology.

vertical flash RAM