Chaparral K5312/K7313 - Manual (Page 139)

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Array Basics
Chaparral’s RAID controllers let you set up and manage disk arrays. A disk array is a
group of disks that appears to the system as a single virtual disk. This is accomplished
through software resident in the RAID controller. RAID (Redundant Array of
Independent Disks) refers to disk arrays in which part of the array storage capacity
may be used to store redundant information. The redundant information lets you
restore user data if a disk in the array fails.
The host system views the controller as a single SCSI disk drive. It is actually an
array of physical disks behind a RAID controller. The controller is managed by
software to appear as a single very large physical disk. Depending on the array type,
the virtual disk has advantages in fault-tolerance, cost, performance, or a combination
of these. This section explains the different array types and the disk requirements for
each type.
Array Types
Array types are defined by their RAID level, a number from 0 through 5 (a higher
RAID level does not necessarily indicate a higher level of performance or fault-
tolerance). Chaparral’s RAID controllers let you create the types of arrays that have
proven to be the most useful for RAID applications: RAID 0, 1, 1/0 (also known as
mirrored), 3, 4, 5, 50, and Volume Sets.
RAID 0 (Striped Disks)
In a RAID 0 array, data is distributed, or striped, across the disks in the array. The
array appears to the server as one large disk with a capacity approximately equal to the
combined capacity of the physical disks. Because multiple reads and writes can be
handled in parallel, the input/output performance of the array is much better than that
of a single physical disk.