A Redundant Disk Array Architecture for Efficient Small Writes
Daniel Stodolsky, Mark Holland, Garth A. Gibson · 1993
Parity encoded redundant disk arrays provide highly reliable, cost effective seconda high performance for reads and large writes. Their performance on small, is writes, much howe worse than mirrored disks — the traditional, highly reliable, but expensive organizat ary storage. Unfortunately, small writes are a substantial portion of the I/O workload of m tant, demanding applications such as on-line transaction processing. This parity paper pr logging, a novel solution to the small write problem for redundant disk arrays. Parity journalling techniques to substantially reduce the cost of e provide small writes. detailed W models of parity logging and competing schemes — mirroring, floating storage, and RAID level 5 — these models by simulation. Parity logging provides performance competitive with mi with capacity overhead close to the minimum offered by RAID, level parity 5. logging Finally can exploit data caching more effectively than all three alternative approaches.