Using serial ata raid – Foxconn 865M06-G-6EKS User Manual
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Appendix
104
865M06 Series User Manual
Using Serial ATA RAID
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 re-
dundant 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 configuration
information of each member is recorded in the reserved sector. That identifies the
drive as a member. All disk members in a formed disk array are recognized 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.
ICH5R supports RAID 0 and 1.
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.