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Appendix
A.3 RAID 1
RAID 1 is commonly referred to as disk mirroring as all data is duplicated
on two or more disks. This provides a high access rate and very high data
availability. RAID 1 has low performance for write operations but very high
performance for intensive read operations.
RAID 1: Mirroring
Characteristics
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•
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Storage capacity = the capacity of the smallest disk
A minimum of two disks are required.
Fault tolerance: Very good
Read transaction rate: Good. Better than a single drive but worse than many
other RAID levels.
Write transaction rate: Worse than a single drive, but better than many other
RAID levels
100% data redundancy means that in the event of disk failure, data can be
copied directly to the replacement without rebuilding.
All the disks contain the same data.
Recommended use
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Accounting
Payroll
Finance
Any application requiring high availability
E
D
FG
C
B
A
CONTROLLER
A
A
B
B
C
D
=
C
D
Figure A-2 RAID 1 disk array
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