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RAID 3 provides increased data transfer rates when data is being
accessed in large chunks or sequentially.
operations that do not span multiple drives, performance is
reduced since the information stored in the parity drive needs to
be re-calculated and re-written every time new data is written to
any of the data disks.
RAID 3 striping with dedicated parity is shown in Figure A- 5.
Logical Drive
Block 1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
Figure A- 5: RAID 3
A.3.6 RAID 5
RAID 5 implements multiple-block striping with distributed
parity. This RAID level offers the same redundancy available in
RAID 3; though the parity information this time is distributed
across all disks in the array. Data and relative parity are never
stored on the same disk. In the event a disk fails, original data can
be reconstructed using the available parity information.
An illustration of RAID 5 striping with non-dedicated parity is
shown in Figure A- 6.
Galaxy 16i User's Manual
Block 1
Block 3
Block 5
Block 7
.
.
.
.
Physical Disks
Dedicated
Striping
Block 2
Parity (1,2)
Block 4
Parity (3,4)
Block 6
Parity (5,6)
Block 8
Parity (7,8)
.
.
However, in write
Parity
.
.
A-7
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