A performance comparison of RAID-5 and log-structured arrays

In this paper, we compare the performance of the well-known RAID-5 arrays to that of log-structured arrays (LSA), on transaction-processing workloads. LSA borrows heavily from the log-structured file system (LFS) approach, but is executed in an outboard disk controller. The LSA technique we examine combines LFS, RAID, compression and non-volatile cache. We look at sensitivity of LSA performance to amount of free space on the physical disks and to the compression ratio achieved. We also evaluate a RAID-5 design that supports compression in cache.