RAID Level 5: Rotating Parity
Explore how RAID 5 improves upon RAID 4 by rotating parity blocks across disks to eliminate bottlenecks. Understand its effects on capacity, failure tolerance, and performance for random reads and writes, and why it has largely replaced RAID 4 in storage systems.
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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 ...