Datasheet

Identifying Motherboards 45
However, if the problem is a bad disk drive, the symptoms aren’t as obvious. As long
as the BIOS POST routines can communicate with the disk drive, they’re usually satisfied.
But the POST routines may not uncover problems related to storing information. Even with
healthy POST results, you may find that you’re permitted to save information to a bad disk,
but when you try to read it back, you get errors. Or the computer may not boot as quickly
as it used to, because the disk drive can’t read the boot information successfully every time.
In some cases, reformatting the drive can solve the problems described in the preceding
paragraph. In other cases, reformatting brings the drive back to life only for a short while.
The bottom line is that read and write problems usually indicate that the drive is malfunc-
tioning and should be replaced soon.
Never low-level-format IDE drives! They’re low-level-formatted from the
factory, and you may cause problems by using low-level utilities on these
types of drives.
SATA and eSATA
Serial ATA (SATA) came out as a standard recently and was first adopted in desktops and
then laptops. Whereas ATA had always been an interface that sends 16 bits at a time, SATA
sends only one bit at a time. The benefit is that the cable used can be much smaller, and
faster cycling can actually increase performance.
External SATA (eSATA) is a variant of SATA that was standardized in 2004 for external
devices. As such, it competes with FireWire and USB, but differs from them in that it requires
its own power connector. The advantage it has over the other technologies is speed—it is
approximately three times faster at data transfer than either FireWire or USB 2.0.
RAID
RAID stands for Redundant Array of Independent Disks. It’s a way of combining the storage
power of more than one hard disk for a special purpose such as increased performance or fault
tolerance. RAID is more commonly done with SCSI drives, but it can be done with IDE drives.
There are several types of RAID, of which you need to know the following three for
the exam:
RAID 0 Also known as disk striping. This is technically not RAID, because it doesn’t pro-
vide fault tolerance. Data is written across multiple drives, so one drive can be reading or
writing while the next drive’s read-write head is moving. This makes for faster data access.
However, if any one of the drives fails, all content is lost.
RAID 1 Also known as disk mirroring. This 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 can be switched to. However, disk mirroring doesn’t help access speed, and
the cost is double that of a single drive.
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