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Chapter 9: Technology Background
RAID 3 – Block Stripe and Dedicated Parity
RAID 3 organizes block data across multiple physical drives and parity data on a
dedicated drive. Generally, RAID Level 3 tends to exhibit lower random write
performance due to the heavy workload of parity recalculation for each I/O.
Heavy I/O loads with a large number of writes tends to work the parity drive
harder in proportion to the other drives in the logical drive.
Promise implements RAID 3 with block-level striping, rather than byte-level
striping.
RAID 3 stripes data across multiple drives with parity on a dedicated drive
Dedicated Parity
Data
Blocks
Physical Drives
The capacity of a RAID 3 logical drive equals the smallest physical drive times
the number of physical drives, minus one. Hence, a RAID 3 logical drive with four
100 GB physical drives will have a capacity of 300 GB. A RAID 3 logical drive
with two 120 GB physical drives and one 100 GB physical drive will have a
capacity of 200 GB.
A RAID 3 on VessRAID consists of 3 to 32 physical drives.
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