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Appendix C RAID
13
RAID
Level
Redundancy
Required
Number of
PDs
Decrease in
Capacity
Advantage Disadvantage
RAID 0 None
1 or
more
*1, *3
None Quick access
Inaccessible when even a
single disk fails
RAID 1
Dual
configuration
2 50%
High reliability
No performance
deterioration in reduced
state
Costly
RAID 5 Parity 3 or more
*4
Equivalent
to capacity
of 1 disk
Concurrent processing for
multiple R/W commands
Parity data read required
for writing
Performance deterioration
in reduced state
RAID6 Double parity 6 or more
*5
Equivalent
to capacity
of 2/6 or
2/10 disks
The most reliable
(redundancy secured on a
failure of one physical disk)
It is necessary to read
parity when writing data.
The accessibility to data
drops on degradation.
RAID10
Dual
configuration
4 or
more
*2, *6
50%
Quick access
High reliability
No performance
deterioration in reduced
state
Costly
RAID50 Parity 10 or more
*7
Equivalent
to capacity
of 1/5 disks
Concurrent processing for
multiple R/W commands
Quick access
It is necessary to read
parity when writing data.
The accessibility to data
drops on degradation.
*1: 100/1000/2000 series disk array: 1, 3, 5, 10, or 15 disks
*2: 100/1000/2000 series disk array: 4, 6, 8, 10, 12, or 14 disks
*3: S400/S1400/S2400/S2800 disk array: Not available for configuration
*4: S400/S1400/S2400/S2800 disk array: 5 disks
*5: S400/S1400/S2400/S2800 disk array: 6 or more disks (4+PQ) and 10 or more (8+PQ)
*6: S400/S1400/S2400/S2800 disk array: 4, 8, or 16 disks
*7: S400/S1400/S2400/S2800 disk array: 10 or 20 disks