Intel KM4AM - Manual (Page 61)

MS-6734 M-ATX Mainboard
4 - 2
This section gives a brief introduction on the RAID-related background knowledge
and a brief introduction on VIA SATA RAID Host Controller. For users wishing to
install their VIA SATA RAID driver and RAID software, proceed to Driver and RAID
Software Installation section.
RAID Basics
RAID (Redundant Array of Independent Disks) is a method of combining two or more
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 redun-
dant 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.
The RAID levels which the VIA VT8237 SATA RAID Host Controller supports are RAID
0 and RAID 1. The table below briefly introduced these RAID levels.
Introduction
RAID Level No. of Drives Capacity Benefits
RAID 0
(Striping)
2 Number drives * 2 Highest performance without data
protection
RAID 1
(Mirroring)
2 Smallest size Data protection
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 64KB. 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.