Ch-2 Storage Devices and Power Supplies
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__are used for permanent storage and quick access. __ typically reside inside the computer, where they are semipermanently mounted with no external access and can hold more information than other forms of storage. __ use a magnetic storage medium and are known as conventional drives to differentiate them from newer solid-state storage media.
Hard disk drive (HDD)
This component controls the drive.
The __controls how the drive operates and how the data is encoded onto the platters. It controls how the data sends signals to the various motors in the drive and receives signals from the sensors inside the drive. Most of todays hard disk technologies incorporate the controller and drive into one assembly.
This is the translator, converting signals from the controller to signals the computer can understand. Most motherboards today incorporate the __ into the motherboards circuitry, offering headers for drive-cable connection.
Host bus adapter (HBA)
Inside the sealed case of the hard drive lie one or more __, where the actual data is stored by the read/write heads.
The __ are mounted on a mechanism that moves them in tandem across both surfaces of all platters. Older drives used a stepper motor to position the __ at discrete points along the surface of the platters, which spin at thousands of revolutions per minute on a spindle mounted to a hub. Newer drives use voice coils for a more analog movement, resulting in reduced data loss because the circuitry can sense where the data is located through a servo scheme, even if the data shifts due to changes in physical disc geometry.
Drive preparation creates concentric rings, or __, which are drawn magnetically around the surface of the platters.
__ are the magnetic domains that represent the smallest units of storage on the discs platters. Magnetic-drive __ commonly store only 512 bytes (1/2 KB) of data each.
The __ of a hard drive is a function of the number of sectors it contains. The controller for the hard drive knows exactly how the sectors are laid out within the disk assembly.
The basic hard disk __ consists of three components: the number of sectors that each track contains, the number of read/write heads in the disk assembly, and the number of cylinders in the assembly. This set of values is known as CHS (for cylinders/heads/sectors).
The number of __ is the number of tracks that can be found on any single surface of any single platter. It is called a cylinder because the collection of all same-number tracks on all writable surfaces of the hard disk assembly looks like a geometric cylinder when connected together vertically. Therefore, cylinder 1, for instance, on an assembly that contains three platters comprises six tracks (one on each side of each platter), each labeled track 1 on its respective surface. Because the number of cylinders indicates only the number of tracks on any one writable surface in the assembly, the number of writable surfaces must be factored into the equation to produce the total number of tracks in the entire assembly. This is where the number of heads comes in.
The following __ have been used in the industry for the platters in conventional magnetic hard disk drives: 5400 rpm 7200 rpm 10,000 rpm 12,000 rpm 15,000 rpm
HDD Speeds/ spin rates
__ have no moving parts but use the same __ memory technology found in the other forms of flash memory. All __ memory is limited to a finite number of write (including erase) operations. Algorithms have been developed to constantly spread the write operations over the entire device. Such wear leveling increases the life of the __, but lack of longevity remains a disadvantage of this technology. __s read contents more quickly, can consume less power and produce less heat, and are more reliable and less susceptible to damage from physical shock and heat production than their magnetic counterparts. However, the technology to build an __ is still more expensive per byte, and SSDs are not yet available in capacities high enough to rival the upper limits of conventional hard disk drive technology.
__ is a magnetic storage medium that uses a diskette made of thin, flexible plastic enclosed in a protective casing. The __ once enabled information to be transported from one computer to another very easily. DD means double density, HD means high density. and ED means extended density.
__ was designed for long-term storage of data. __ are read-only, meaning that information written in the factory cant be erased or changed.
__ disc is a single-sided disc that has a single layer of encoded information. These discs have a capacity of 4.7GB. By adding another media surface on the side of the disc where the label is often applied, a double-sided disc is created. Such double-sided discs have a capacity of 9.4GB.
CD-ROM drives are rated in terms of their data transfer speed. The first CD-ROM drives transferred data at the same speed as home audio CD players, 150KBps, referred to as 1X. Soon after, CD drives rated as 2X
drives that would transfer data at 300KBps appeared. They increased the spin speed in order to increase the data transfer rate. This system of ratings continued up until the 8X speed was reached. At that point, the CDs were spinning so fast that there was a danger of them flying apart inside the drive. So, although future CD drives used the same rating (as in 16X, 32X, and so on), their rating was expressed in terms of
theoretical maximum transfer rate; 52X is widely regarded as the highest multiplier for data CDs. The standard DVD-ROM 1X transfer rate is 1.4MBps, already nine times that of the comparably labeled CD-ROM. As
a result, to surpass the transfer rate of a 52X CD-ROM drive, a DVD-ROM drive need only be rated 6X. DVD transfer rates of 16X at the upper end of the scale are common. The 1X transfer rate for Blu-ray is 4.5MBps,
roughly 3 1?4 times that of the comparable DVD multiplier and close to 30 times that of the 1X CD transfer rate. It takes 2X speeds to properly play commercial Blu-ray videos.
Optical Drive Data Rates
The equipment used to read the resulting discs employs a violet laser, in contrast to the red laser used with standard DVD and CD technologies. __ technology storage capacity is 25GB on the basic disc. When you add a second layer to the same or opposite side of the disc, you attain 50GB of storage.
Increasing the power of the laser allowed the crystalline media surface to be melted and changed in such a way that light would reflect or refract from the surface in microscopic increments. This characteristic allowed mimicking of the way in which the original CD-ROM discs stored data. Eventually, discs that could be written to, erased, and rewritten were developed. The original two levels closely matched those of the writable discs and drives. The third level, somewhere in between, could neutralize the crystalline material without writing new information to the disc. This medium level of power left the disc surface in a state similar to its original, unwritten state. Subsequent high-power laser usage could write new information to the neutralized locations.
Recordable Discs and Burners
CD-recordable (CD-R) and CD-rewritable ( CD-RW ) drives are essentially CD-ROM drives that allow users to create their own CD-ROMs. They look very similar to CD-ROM drives but feature a logo on the front panel that represents the drives CD-R or CD-RW capability.
Recordable CD Formats
A DVD burner is similar to a CD-R or CD-RW drive in how it operates: It can store large amounts of data onto a special, writable DVD. Single-sided, dual-layer (DL) discs can be used to write 8.5GB of information to one single-sided disc. Common names for the variations of DVD burning technologies include DVD+R, DVD+RW, DVD-R, DVD-RW, DVD-RAM, DVD-R DL, and DVD+R DL. The plus standards come from the DVD+RW Alliance, while the dash counterparts are specifications of the DVD Forum. The number of sectors per disc varies between the plus and dash variants, so older drives might not support both types. The firmware in todays drives knows to check for all possible variations in encoding and capability. The plus variants have a better chance of interoperability, even without the disc being finalized.
Recordable DVD Formats
Purchased blank; able to be written to and erased just like a hard or floppy disk; no session to close before subsequent access to stored data
__ is a way of combining the storage power of more than one hard disk for a special purpose, such as increased performance or fault tolerance. __ can be implemented in software or in hardware, but hardware __ is more efficient and offers higher performance at an increased cost.
Redundant Array of Independent Disks RAID
Also known as disk mirroring. __ is a method of producing fault tolerance by writing all data simultaneously to two separate drives. If one drive fails, the other contains all the data and will become the primary drive. However, disk mirroring doesnt help access speed, and the cost is double that of a single drive. If a separate host adapter is used for the second drive, the term duplexing is attributed to __. Only two drives can be used in a __ array.
__Combines the benefits of both RAID 0 and RAID 1, creating a redundant striped volume set. Unlike RAID 1, however, __ does not employ mirroring for redundancy. Each stripe places data on n 1 disks, and parity computed from the data is placed on the remaining disk. The parity is interleaved across all the drives in the array so that neighboring stripes have parity on different disks. If one drive fails, the parity information for the stripes that lost data can be used with the remaining data from the working drives to derive what was on the failed drive and rebuild the set once the drive is replaced. Recomputing parity for these stripes is required only when rebuilding the array. A minimum of three drives is required for RAID 5.
An older form of removable storage is the __. __ devices can be installed internally or externally and use either a digital or analog magnetic tape medium instead of disks for storage. They hold much more data than any other medium but are also much slower. They are primarily used for batch archival storage, not interactive storage.
Tape Backup Devices
Once only for primary memory usage, the same components that sit on your motherboard as RAM can be found in various physical sizes and quantities in todays solid-state storage solutions. These include older removable and nonremovable flash memory mechanisms, Secure Digital (SD) cards and other memory cards, and USB flash drives. Each of these technologies has the potential to reliably store a staggering amount of information in a minute form factor. Manufacturers are using innovative packaging for some of these products to provide convenient transport options (such as keychain attachments) to users.
__ are incredibly versatile and convenient devices that allow you to store large quantities of information in a very small form factor. Many such devices are merely extensions of the hosts USB connector, extending out from the interface but adding little to its width, making them easy to transport, whether in a pocket or laptop bag. USB flash drives capitalize on the versatility of the USB interface, taking advantage of the Plug and Play feature and the physical connector strength. Upon insertion, these devices announce themselves to Windows Explorer as removable drives and show up in the Explorer window with a drive letter. This software interface allows for drag-and-drop copying and most of the other Explorer functions performed on standard drives.
USB Flash Drives
USB, FireWire and eSATA present higher performance options.
Externally Attached Drives
You can insert and remove the device with the system powered on. Most USB-attached devices without a file system fall into this category. Non-hot-swappable devices, in contrast, either cannot have the systems power applied when they are inserted or removed or they have some sort of additional conditions for their insertion or removal.
RAID systems benefit from devices and bays with a single connector that
contains both power and data connections instead of two separate
connectors. This is known as __.
Single Connector Attachment SCA
__ include USB flash drives and external drives that have a file system. Windows and other operating systems tend to leave files open while accessing them and write cached changes to them at a later time, based on the algorithm in use by the software. Removing such a device without using the Safely Remove Hardware utility can result in data loss. However, after stopping the device with the utility, you can remove it without powering down the system, hence the warm component of the categorys name.
A __ converts 110V or 220V AC current into the DC voltages that a computer needs to operate. These are +3.3VDC, +5VDC, 5VDC (on older systems), +12VDC, and 12VDC. The jacket on the leads carrying each type of voltage has a different industry-standard color coding for faster recognition. Black ground leads offer the reference that gives the voltage leads their respective magnitudes. The +3.3VDC voltage was first offered on ATX motherboards. __ are rated in watts. The higher the number, the more power your computer can draw from the power supply. Think of this rating as the capacity of the device to supply power.
The standard peripheral power connector is generally used to power different types of internal disk drives. This type of connector is also called a__.
Floppy drive power connectors are most commonly used to power floppy disk drives and other small form factor devices. This type of connector is smaller and flatter than any of the other types of power connectors. These connectors are also called __. Notice that there are four wires going into this connector. These wires carry the two voltages used by the logic circuits and motors: +5VDC (carried on the red wire) and +12VDC (carried on the yellow wire), respectively; the two black wires are ground wires
ATX, ATX12V, and EPS12V ConnectorsWith ATX motherboards came a new, single connector from the power supply.PCI Express has power requirements that the ATX connector could not satisfy, leading to different connectors with different versions of the more advanced __ specifications, which have gone through four 1.x versions and already five 2.x versions. Throughout the versions of __, additional 4-, 6-, and 8-pin connectors supply power to components of the motherboard and its peripheralssuch as network interfaces, PCIe cards, specialty server components, and the CPU itselfthat require a +12V supply in addition to the +12V of the standard ATX connector. These additional connectors follow the __ and __ standards.
ATX12V and EPS12V
The ATX connector was further expanded by an additional four pins in__. The original ATX system connector (also known as the ATX motherboard power connector) feeds an ATX motherboard. It provides the six voltages required, plus it delivers them all through one connector: a single 20-pin connector. This connector is much easier to work with than the dual connectors of the AT power supply.
When the Pentium 4 processor was introduced, it required much more power than previous CPU models. It was decided to deliver 12V at lower amperage to a voltage regulator module (VRM) near the CPU. The higher current at a lower voltage was possible at that shorter distance from the CPU. As a result of this shift, motherboard and power supply manufacturers needed to get this more varied power to the system board. The solution was the __ standard, which added two supplemental connectors. One was a single 6-pin auxiliary connector similar to the P8/P9 AT connectors that supplied additional +3.3V and +5V leads and their grounds. The other was a 4-pin square mini-version of the ATX connector, referred to as a P4 (for the processor that first required them) connector, that supplied two +12V leads and their grounds.
__ uses an 8-pin version, called the processor power connector, that doubles the P4s function with four +12V leads and four grounds. Figure 2.29 illustrates the P4 connector. The 8-pin processor power connector is similar but has two rows of 4 and, despite its uncanny resemblance, is keyed differently from the 8-pin PCIe power connector to be discussed shortly.
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