Promise Technology Pegasus32 R4, Product Manual

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Technology Background Pegasus32 Product Manual
RAID 1 – Mirror
When a logical drive is mirrored, identical data is written to a pair of physical drives, while reads are
performed in parallel. The reads are performed using elevator seek and load balancing techniques
where the workload is distributed in the most efficient manner. Whichever drive is not busy and is
positioned closer to the data is accessed first.
With RAID 1, if one physical drive fails or has errors, the other mirrored physical drive continues to
function. Moreover, if a spare physical drive is present, the spare drive is used as the replacement drive
and data begins to mirrored to it from the remaining good drive.
RAID 1 Mirrors identical data to two drives
The logical drive’s data capacity equals the smaller physical drive. For example, a 100 GB physical
drive and a 120 GB physical drive have a combined capacity of 100 GB in a mirrored logical drive.
If physical drives of different capacities are used, there is unused capacity on the larger drive.
RAID 1 logical drives on Pegasus consist of two physical drives.
If you want a mirrored logical drive with more than two physical drives, see “RAID 1E – Enhanced
Mirror”.
Physical Drives
Data Mirror