MSI 915P COMBO-FR User Guide - Page 105
RAID 1 Mirroring, RAID 0+1 Striping/Mirroring, JBOD Spanning
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Introduction to VIA VT6410 IDE RAID 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 0+1 (Striping/Mirroring) RAID 0+1 is a combination of RAID 0 and RAID 1 array types. A minimum of four drives needs to be installed. With a four-drive array, there must be two pairs of RAID 0 drives. Each pair mirrors the data on the other pair of striping drives. The data capacity is two times the smallest drive. In a four-drive array, a single drive failure will cause the whole array to become, in essence, a RAID Level 0 array. However, this does not impact the data access. Another unique feature of RAID 0+1 is dual fault tolerance. In some cases, two drives can fail simultaneously and still maintain the integrity of the data. The data can still be accessed and worked like a RAID 0 array. Assume the drives are configured as follows (M = Master, S = Slave, A/B indicates which striping pair the drive belongs to, number indicates which part of stripe data): IDE 2 IDE 3 M Drive A1 Drive A2 S Drive B1 Drive B2 In a RAID 0+1 array, the data integrity will remain if any 1, 2 combination survives. The following table indicates the possible combination of dual drive failure and the respective results of each case. Failed Drives Array Status Note A1, A2 B1, B2 A1, B2 B1, A2 A1, B1 A2, B2 Working Working Working Working Failure Failure B1, B2 retains array integrity A1, A2 retains array integrity B1, A2 retains array integrity A1, B2 retains array integrity A2, B2 contains only half of array data A1, B1 contains only half of array data JBOD (Spanning) A spanning disk array is equal to the sum of the all drives when the drives used are having different capacities. Spanning stores data onto a drive until it is full, then proceeds to store files onto the next drive in the array. When any disk member fails, the failure affects the entire array. JBOD is not really a RAID and does not support fault tolerance. 6-3