System information

Appendix
A-3
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
• 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
• Accounting
• Payroll
• Finance
• Any application requiring high availability
A
A
B
C
D
A
B
C
D
CONTROLLER
B
C
G
F
D
E
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Figure A-2 RAID 1 disk array