Raid 1 - Rorke Data Galaxy 16i User Manual

Logical Drive
Figure A- 2: RAID 0
A.3.3 RAID 1
RAID 1 implements disk mirroring where a copy of the same data
is recorded onto two sets of striped drives. By keeping two copies
of data on separate disks or arrays, data is protected against a disk
failure. If, at any time, a disk on either side fails, the remaining
good disk (copy) can provide all of the data needed, thus
preventing downtime.
In disk mirroring, the total disk capacity is equivalent to half the
sum of the capacities of all drives in the combination. Thus,
combining four 1GB SATA drives, for example, would create a
single logical drive with a total disk capacity of 2GB. This
combination of drives appears to the system as a single logical
drive.
NOTE
One drawback to RAID 1 is that it does not allow running
expansion. Once a RAID 1 array has been created, to expand it,
the data must be backed up elsewhere before a new drive can be
added. Other RAID levels permit running expansion.
RAID 1 is simple and easy to implement; however, it is more
expensive as it doubles the investment required for a non-
redundant disk array implementation.
A-4
Block 1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
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Physical Disks
Striping
Block 1 Block 2
Block 3 Block 4
Block 5 Block 6
Block 7 Block 8
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Galaxy 16i User's Manual
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