n Level 1 provides much better write performance than level 5
l Level 5 requires at least 2 block reads and 2 block writes to write a single block, whereas Level 1 only requires 2 block writes
l Level 1 preferred for high update environments such as log disks
n Level 1 had higher storage cost than level 5
l disk drive capacities increasing rapidly (50%/year) whereas disk access times have decreased much less (x 3 in 10 years)
l I/O requirements have increased greatly, e.g. for Web servers
l When enough disks have been bought to satisfy required rate of I/O, they often have spare storage capacity
so there is often no extra monetary cost for Level 1!
n Level 5 is preferred for applications with low update rate,
and large amounts of data
n Level 1 is preferred for all other applications