Raid : an overview
A redundant array of independent disks (RAID) is a
configuration of two or more disk drives designed to provide improved
performance and, in one setup, to recover automatically from a failure.
Most commonly used in server applications, RAID can also provide
enhanced performance and security for personal computers. RAID systems
can be implemented at two different levels: RAID 0 and RAID 1.
RAID 0
RAID 0 provides data stripping – it takes data that needs to be stored
and distributes it evenly between two or more hard drives. Because the
system considers the two hard drives as one logical hard drive, the
data is stored only once.
In a two-drive setup, for example, RAID 0 saves and accesses data
quickly and efficiently. Rather than one bit at a time, RAID 0 stores
and retrieves two bits of data simultaneously. Theoretically, the time
it takes to save and access information is cut in half over a single
drive system.
RAID 0 is popular for video and image production and editing,
pre-press applications, and other applications requiring high
bandwidth. However, RAID 0 does not provide fault tolerance – if one
drive fails, the information on it is lost.
RAID 1
RAID 1 provides “disk mirroring,” which copies the same data onto two
or more drives. Unless the system uses RAID 1 with duplexing, both
drives must use the same adapter card.
Unlike RAID 0, RAID 1 allows for fault tolerance. Since the same data
is saved twice, if one hard drive fails the second has a complete copy
of all information saved. While not as fast as RAID 0, RAID 1 retrieves
data more efficiently than a single drive setup because information is
gathered in from more than one location.
RAID 1 is popular for accounting, payroll, financial, and
other applications that require high availability and higher relative
data security. However, RAID 1 writes data once in each drive, which
makes saving data less efficient and halves drive capacity.
Setting Up RAID
To use RAID, a system’s motherboard must have an onboard RAID
controller or a PCI-connected RAID controller. Additionally, its hard
drives must be compatible with the motherboard, and preferably all of
the same brand, model, and size. Most RAID-controller-equipped
motherboard manuals describe how to set up RAID, and many ship with
user-friendly setup utilities.
