User Guide

VT6410 User Manual – IDE RAID Controller
Preliminary Revision 0.2, November 11, 2002 2 Introduction
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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 1 IDE 2
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 Working B1, B2 retains array integrity
B1, B2 Working A1, A2 retains array integrity
A1, B2 Working B1, A2 retains array integrity
B1, A2 Working A1, B2 retains array integrity
A1, B1 Failure A2, B2 contains only half of array data
A2, B2 Failure A1, B1 contains only half of array data