Promise Technology 2-Year Extended Warranty for VessR2000 RAID Head - Manual (Page 581)

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Vess R2000 Series Product Manual Promise Technologies
RAID 1 – M
IRRoR
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.
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 Vess consist of two physical drives.
If you want a mirrored logical drive with more than two physical drives, see “RAID 1E – Enhanced
Mirror” on page 556.
RAID 1 Mirrors identical data to two drives
Data Mirror
Physical Drives