Hardware Reference
In-Depth Information
(2 1/2-inch) hard disks barely sip electrical power and actually use 1 watt or less!
Configuration Items
To configure a PATA HDD for installation in a system, you may have to set several jumpers
properly. SATA drives generally don't need any configuration; however, in some rare cases a jumper
may need to be placed to force a SATA drive to use a lower interface transfer rate. This is a rare
problem that happens only with some drives and older SATA host adapter chipsets.
See
Chapter 7
,
“
The ATA/IDE Interface
,”
p.
377
.
Hard Disk Features
To make the best decision in purchasing a hard disk for your system or to understand what
distinguishes one brand of hard disk from another, you must consider many features. This section
examines some of the issues you must consider when you evaluate drives:
• Capacity
• Performance
• Reliability
• Cost
Capacity
As stated earlier, a corollary of Parkinson's famous “law” can be applied to hard drives: “Data
expands so as to fill the space available for its storage.” This, of course, means that no matter how
big a drive you get, you
will
find a way to fill it.
If you've exhausted the space on your current hard disk, you might be wondering, “How much storage
space is enough?” Because you are more likely to run out of space than have too much, you should
aim high and get the largest drive that will fit within your budget. Modern systems are used to store
many space-hungry file types, including digital photos, music, video, newer OSs, applications, and
games. Photo, audio, and especially video files can take up huge amounts of storage, easily running
into hundreds of gigabytes or even terabytes of storage. Although most drives today can hold hundreds
of gigabytes, many people are storing several times that.
Running out of space causes numerous problems in a modern system, mainly because Windows, as
well as many newer applications, uses a large amount of drive space for temporary files and virtual
memory. When Windows runs out of room, system instability, crashes, and data loss are inevitable.
Capacity Limitations
How big a hard drive you can use depends on many factors, including the interface, drivers, OS, and
file system you choose.
When the ATA interface was created in 1986, it had a maximum capacity limitation of 137GB
(65,536×16×255 sectors). BIOS issues further limited capacity to 8.4GB in systems produced earlier
than 1998, and as low as 528MB in systems earlier than 1994. Even after the BIOS issues were
resolved, however, the initial 137GB limit of ATA remained. Fortunately, this was broken in the
ATA-6 specification drafted in 2001. ATA-6 augmented the addressing scheme used by ATA to
allow drive capacity to grow to 144PB (petabytes, or quadrillion bytes), which is 248 sectors. This
has opened the door allowing PATA and SATA drives over 137GB to be released.
