RAID User’s Guide
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Intel ICH6R SATA RAID
1. Introduction
RAID (Redundant Array of Independent Disks) is a method of combining two hard
disk drives into one logical unit. The advantage of an Array is to provide better
performance or data fault tolerance. Fault tolerance is achieved through data
redundant operation, where if one drives fails, a mirrored copy of the data can be
found on another drive. This can prevent data loss if the operating system fails or
hangs. The individual disk drives in an array are called members. The configura-
tion information of each member is recorded in the reserved sector. That identi-
fies the drive as a member. All disk members in a formed disk array are recog-
nized as a single physical drive to the operating system.
Hard disk drives can be combined together through a few different methods. The
different methods are referred to as different RAID levels. Different RAID levels
represent different performance levels, security levels and implementation costs.
RAID 0 (Striping)
RAID 0 reads and writes sectors of data interleaved between multiple drives. If
any disk member fails, it affects the entire array. The disk array data capacity is
equal to the number of drive members times the capacity of the smallest member.
The striping block size can be set from 4KB to 128KB. RAID 0 does not support
fault tolerance.
RAID 1 (Mirroring)
RAID 1 writes duplicate data onto a pair of drives and reads both sets of data in
parallel. If one of the mirrored drives suffers a mechanical failure or does not
respond, the remaining drive will continue to function. Due to redundancy, the
drive capacity of the array is the capacity of the smallest drive. Under a RAID 1
setup, an extra drive called the “spare drive” can be attached. Such a drive will be
activated to replace a failed drive that is part of a mirrored array. Due to the fault
tolerance, if any RAID 1
drive fails, data access will not be affected as long as
there are other working drives in the array.
ＲＡＩＤ Ｍａｎｕａｌ．ｐ６５
2005-1-21, 10:29
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