Promise Technology UltraTrak100 TX8 - Manual (Page 49)

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RAID 0+1 – S
TRIPING
/M
IRROR
Striping/mirroring combines both of the previous array types. It can increase
performance by reading and writing data in parallel while protecting data with
duplication. At least four drives are needed for RAID0+1 to be installed. With a
four-drive disk array, drive pairs are striped together with one pair mirroring the
first pair. The data capacity is similar to a standard mirroring array, with half of the
total storage capacity dedicated for redundancy. An added plus for using RAID
0+1 is that, in many situations, such an array offers double fault tolerance. Double
fault tolerance may allow your data array to continue to operate depending on
which two drives fail.
Figure A3. RAID 0+1 striping and mirroring of two drive pairs