Disk arrays and other mass storage devices differ from
most computer systems in their incorporation of mechanical elements,
namely disks or tapes or in the future MEMS based storage devices. We
will concentrate our attention on disk based mass storage devices,
namely disk arrays. We shall explore some of the research aimed at
minimizing the amount of mechanical movement involved in servicing
user requests. A second theme which is central to the discussion of
disk array performance is parallelism, since disk arrays contain many
devices, again disks, which can act in parallel.
Trying to optimize a disk array's performance along one of these
themes may hurt the other. In many cases though these goals are
The main techniques we will describe are : Caching, choice of data
layout the use of mirroring and disk queueing.
We will also briefly discuss basic models for the host request stream
since such models are essential for producing any results.