 Hard
Drive Storage
Over
the past couple of years, there has been quite a revolution in storage
technology. Cost has plummeted, performance has increased, and several
sophisticated connection technologies (such as FireWire) have appeared.
Now that hard drives have come down in price to where they are very affordable,
the question is not whether to buy additional hard drives, but instead,
what kind of drives, how large, and with what connection technology.
I plan on adding external hard drives to several
computers. Which one of the protocols available should I use to connect
the hard drives?
Any of the following technologies
are fine. However, each one is designed for a slightly different price/performance
niche and has different strengths and weaknesses.
- Universal Serial Bus
(USB) is designed to connect slower devices, such as keyboards,
mice, Zip drives, and inexpensive scanners. Because it is slow, it is
not a great technology for connecting hard drives.
- ATA (AT Attachment)
and IDE (Integrated Drive Electronics) are the same thing: a
disk drive connection scheme designed to integrate the controller into
the drive to reduce interface costs. ATA's various implementations only
support two drives per controller.
- SCSI (Small Computer
System Interface) is a series of computer bus protocols that support high data throughput and multiple devices per controller (between 7 and 15 devices, depending on the kind of SCSI). SCSI is a great hard drive connection protocol that is more reliable (and more expensive) than ATA.
- FireWire, Apple's
licensed name for the IEEE 1394 connection protocol, is a high speed
connection protocol originally designed for digital video devices. It
is also becoming popular for storage devices, because it is hot pluggable
(you don't have to turn off the machine to plug it in), supports up
to 63 devices per controller, and can negotiate and maintain a fixed
amount of bandwidth between any two devices in the chain. Before purchasing
any hard drives, be sure to reference the user guide that came with
your computer.
 What
is RAID storage and when do I need it? 
A Redundant Array of Inexpensive
Disks (RAID) is a way of speeding up hard drive performance, increasing
hard drive reliability, or both by putting three or more hard drives together
and treating them as one.
Most single hard drives can't
support higher than 12 Megabytes per second transfer rates, even though
most protocols (SCSI, ATA and FireWire) can support much higher rates.
By adding multiple drives together in a RAID configuration, you can get
higher throughput.
A RAID solution is a good
idea if you do a lot of Photoshop work and have already optimized the
rest of your computer, because disk reads and writes will slow you down.
Otherwise, RAID solutions are usually used for digital video editing and
server applications. Most publishing workstations don't need them.
Technically, there are six
different RAID configurations, Level 0 through 5. However, Level 0 is
not really RAID because it consists of striping data across multiple drives.
This results in very fast performance, but no redundancy (if any one drive
crashes, you lose all the data on the RAID).
Conversely, RAID Level 1 just
mirrors the data, making it redundant but not much faster than a single
drive. RAID Level 2 is not usually used. Which leaves Levels 3, 4 and
5, all of which improve performance and redundancy by saving parity information
as well as data. Parity information allows the RAID array to rebuild the
data on any one drive should it fail. Levels 3 and 4 put all the parity
data on one drive, while Level 5 stripes the parity information across
all drives.
 I
am considering buying a Macintosh G4 for desktop publishing. Do I need
the optional Ultra-SCSI card?
In most cases, no. All G4's
come with FireWire connections which should provide fast enough data transfer
speed. Instead, consider buying the $50 SCSI card for compatibility with
scanners and removable drives. The stock ATA drives that come in most
G4s are very fast and if you really need the performance that UltraWide
SCSI provides, you will need a RAID.
 I
am buying a Windows NT workstation for desktop publishing. Should I purchase
a 1394 (FireWire) card to add peripherals?
FireWire for PC's is not particularly
well established, except for digital video applications. In other words,
some FireWire peripherals may not work with some FireWire cards (this
also can occur on the Mac if you use a FireWire card other than Apple's).
Therefore, consider an Adaptec SCSI card instead. These are cheaper for
PCs than Macs and provide good performance and compatibility.
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