RAID Level 5: Rotating Parity
This lesson presents RAID level 5, an improvement over level 4, and analyzes it with respect to the capacity, reliability, and performance.
We'll cover the following...
To address the small-write problem (at least, partially), Patterson, Gibson, and Katz introduced RAID-5. RAID-5 works almost identically to RAID-4, except that it rotates the parity block across drives. Look at the figure given below:
As you can see, the parity block for each stripe is now rotated across the disks, in order to remove the parity-disk bottleneck for RAID-4.
RAID-5 Analysis
Much of the analysis for RAID-5 is identical to RAID-4. For example, the effective capacity and failure tolerance of the two levels are identical. So are sequential read and write performance. The latency of a single request (whether a read or a write) is also the same as RAID-4.
Random read performance
Random read ...