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Circular Storage: Hard Disks and Optical Drives | View information about Circular Storage: Hard Disks and Optical Drives within our Technology Website Directory section by reviewing this area of our website. We provide a wealth of information online to help our visitors become better informed about Computer Buzz. |
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Circular Storage: Hard Disks and Optical Drives
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For most home computer users, storage media boil down to two main categories: hard disks (HDs) and optical disks (CDs and DVDs). There are other choices, of course, like tape drives and flash drives, but HDs and opticals are really the big ones. Computer Buzz has taken a close look at both of them.
There are currently three broad types of hard disks available either as OEM or aftermarket products. These are: Advanced Technology Attachment (ATA), Serial ATA (SATA; rhymes with "beta"), and SCSI (pronounced "scuzzy").
The largest hard drive you could buy in 2007 was 1 terabyte (TB). Four-TB drives are predicted to be available by 2009. The standard speed of most hard drives in 2007 was 7200 rpm, but 10,000-rpm drives are available, and you can even find a few that run at 15,000 rpm. Problem is, at this point in hard drive development, you must trade off speed for capacity, i.e., slow drives hold more data, and fast-spinning drives hold less. That may change in the future.
The vast majority of all hard disks on Earth are made by the following manufacturers:
Compaq/HP Official Website: www.HP.com
Fujitsu Official Website: www.Fujitsu.com
Hitachi Official Website: www.Hitachi.us
Seagate/Maxtor Official Website: www.Seagate.com
Samsung Official Website: www.Samsung.com
Western Digital Official Website: www.wdc.com/en/
Optical disks come in two flavors, CDs and DVDs.
The technical specs of storage media are mind-boggling, but we'll try to stick to the important points and keep this discussion brief and comprehensible.
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ATA (aka PATA, IDE, EIDE, etc.) Hard Drives
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Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks and CD-ROM drives inside personal computers. It is rarely, if ever, used to connect external devices. ATA was developed in 1986 by Western Digital specifically for use with IBM's then-new PC AT computer.
Many synonyms and near-synonyms for ATA exist, including abbreviations such as IDE and ATAPI. Also, with the market introduction of Serial ATA (SATA) in 2003, the original ATA was retroactively renamed Parallel ATA (PATA). The terms IDE and EIDE are often used interchangeably with ATA, although they not the same thing.
The ATA interface at first worked only with hard disks, but eventually an extended standard came to work with a variety of other devices—generally those using removable media. Principally, these devices include CD-ROM and DVD-ROM drives, tape drives, and large-capacity floppy drives such as the Zip drive and SuperDisk drive. The extension bears the name AT Attachment Packet Interface (ATAPI).
Until the introduction of serial ATA, 40-pin connectors generally attached drives to a ribbon cable. Each cable has two or three connectors, one of which plugs into an adapter on the mother board. The remaining one or two connectors plug into drives. Parallel ATA cables transfer data 16 bits at a time.
(Refer to adjacent photo of ATA 40-pin ribbon cable.)
If two devices attach to a single cable, one is commonly referred to as a master and the other as a slave. The master drive generally appears first when the computer's BIOS and/or operating system goes to look for available drives. If there is a single device on a cable, in most cases it should be configured as master. However, some hard drives have a special setting called “single” for this configuration. These settings can be easily configured by the use of well-labelled jumpers on the rear of the drive.
A drive setting called “cable select” has come into widespread use; a drive set to cable select will automatically configure itself as master or slave, according to its position on the cable.
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Serial ATA (aka SATA) Hard Drives
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Serial ATA (SATA) is a computer bus primarily designed for transfer of data between a computer and storage devices such as hard disks or optical drives.
The main benefits are thinner cables that let air cooling work more efficiently, faster transfers, ability to remove devices while operating (hot swapping), and more reliable operation with tighter data integrity checks.
SATA was designed as a successor to the legacy Advanced Technology Attachment standard (ATA) and is expected to eventually replace the older technology (retroactively renamed Parallel ATA or PATA). Serial ATA adapters and devices communicate over a high-speed serial link.
SATA uses only 4 signal lines, allowing for much more compact (and inexpensive) cables compared with PATA. It also offers new features such as hot-swapping and native command queuing.
(Refer to adjacent photo of SATA data connector.)
The SATA power and data cables are the most noticeable change from Parallel ATA. Unlike Parallel ATA, the same physical connectors are used on 3.5-inch (90 mm) desktop hard disks and 2.5-inch (70 mm) notebook disks. This eliminates the need for a mechanical adapter when using a notebook drive in a desktop computer.
The SATA standard also specifies a new power connector. Like the data cable, it is wafer-based, but its wider 15-pin shape prevents accidental misidentification and forced insertion of the wrong connector type.
At the device level, SATA and PATA devices are completely incompatible and cannot be interconnected.
SATA is designed to be backwards and forwards compatible with future revisions of the SATA standard.
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SCSI Hard Drives
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SCSI (Small Computer System Interface) is a set of standards for physically connecting and transferring data between computers and peripheral devices. SCSI is most commonly used for hard disks and tape drives, but it can connect a wide range of other devices, including scanners, and optical drives (e.g., CD, DVD). SCSI buses also allow connection of several drives (using multiple channels, 7 or 15 on each channel) whereas SATA allows one drive per channel, by design. SCSI currently offers transfer rates higher than SATA, but SCSI is a more complex bus usually resulting in higher manufacturing cost.
Since its standardization in 1986, SCSI has been commonly used in the Amiga, Apple Macintosh, and Sun Microsystems computer lines and PC server systems. Apple dropped on-board SCSI completely (in favor of ATA and FireWire) with the Blue & White G3 Power Mac desktop in 1999. SCSI has never been popular in the low-priced PC world, owing to the lower cost and reasonably adequate performance of that market's ATA hard disk standard.
SCSI is the faster interface, which takes a load off of your CPU and allows for better multitasking.. Consequently, SCSI hardware is preferred in enterprises for server purposes. The MTBF of SATA drives is usually about 600,000 hours, while SCSI drives are commonly rated at upwards of 1,500,000 hours!
Other reasons to go SCSI are if you want a lot of devices (you can easily have 15 devices, IDE used to only allow for 4, but newer motherboards come with extra connectors, but still only allow for 2 devices per cable) or you really need the high speed 10,000- 15,000-RPM drives.
Perhaps the most important numbers to consider in terms of rapid data transfer are the RPMs of the hard drive. The most common rotational speeds for IDE drives are 5400 RPM, 7200 RPM, and now some at 10,000 RPM. If you can afford it, get the Serial ATA drives that run at 10,000 RPM. For SCSI, the RPMs are usually at 7200 or 10,000, with some newer drives as high as 15,000 RPM. Just remember: speed costs money—how fast do you want to go?
Internal SCSI cables are usually ribbon cables that have two or three 68-pin or 50-pin connectors. The 50-pin connectors are the more common. External cables are shielded and only have connectors on the ends.
(Refer to adjacent photo of SCSI hard disk with 68-pin data connector on the left and 4-pin Molex power connector on the right.)
Some drive manufacturers offer longer warranties for SCSI devices, indicating a higher manufacturing quality control of SCSI devices compared to PATA/SATA devices. Most ATA hard drives have a 1- to 3-year warranty, whereas most SCSI drives have a 5- year warranty.
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Compact Disks (CDs)
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As you know, compact disk drives come in two flavors: read only (CD-ROM) and read/write (CD-R/RW). Most software apps are distributed on CDs now, and virtually all commercial music is. A CD can store 700 MB of data. However, the handwriting is on the wall for the 700-Meg CD. It is a very mature technology, and in a few short years, it will only be found on museum shelves, probably right next to the 1.44-Meg floppy. But for the moment, it is still the standard we use to reproduce music.
Apple and Sun Microsystems have used 50-pin SCSI CD drives in their hardware (for superior speed), but just about everyone else has chosen the 40-pin ATA (or SATA) units.
The speed of the drive is expressed as an x-number, meaning the relative speed of its ability to transmit data as compared to the data speed of a conventional music CD. A music CD has an arbitrarily assigned speed of “1” (or “1x”). Most currently available CD drives are rated at 48x or better, the best ones at 52x.
CD-R/RW drives (aka burners, writers) also allow a user to create their own CDs of music and/or other data. These drives are fine for everything for which you would use a CD-ROM, and you can also use it for backup purposes (e.g., the data on your computer's hard drive or your music CDs) and for creating your own bootleg music CDs.
Almost all brands of CDs will work just fine in all brands of CD drives. As for the drives themselves, two CD brand names stand out: Plextor and Lite-On. Plextor is quite expensive; Lite-On is refreshingly cheap. Both are excellent quality drives which Computer Buzz highly recommends.
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Digital Video Disks (DVDs)
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DVDs (Digital Video Disks or Digital Versatile Disks) can store up to 4700 MB (4.7 GB) of data, as opposed to only 700 MB for a conventional CD. The two media are the exact same physical size, and you have to look carefully to tell one disk from the other.
DVD drives can also read CDs, so you don't really need a separate CD-ROM drive. Moreover, DVD drives have come down enough in price so that there isn't much point in purchasing a CD-ROM drive any more. Several companies now make CD burner drives that will also read DVDs (or would that be DVD reader drives that also burn CDs?).
Perhaps DVDs' most practical use is the distribution of movies for home theater consumption. The DVD format allows for much higher resolution digital recording that looks much clearer than the virtually defunct VCR tape recordings.
DVD disks are available in a couple of different and extremely confusing formats: DVD-R and DVD+R with an RW (ReWrite) version of each also available. Until a Higher Power steps in and gets this mess straightened out, Computer Buzz strongly recommends that, for safety's sake, you patronize only DVD-R and DVD-RW disks. DVD-R was the original video disk standard. And by the way, that “-” between the D and the R is a hyphen, NOT a minus sign. Stay away from any optical disk that has a “+” anywhere in its name.
As of now, most DVD burners on the market are "single layer" units that hold about 4.7 GB on one side. But "dual layer" DVDs have been introduced recently. They contain a second layer of laser-accessible recording media just below the first and can hold a total of 8.5 GB of data on one side. Or, you can purchase single layer, dual sided DVDs that hold 4.7 GB on each side for a total of 9.4 GB. If that's not enough, you can now purchase double-sided, dual layer DVDs that hold 8.5 GB on each side for a total of 17GB. It is unclear where all this is going to end; just be sure to purchase the appropriate disks for whatever type of DVD drive you're using.
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