On 01/08/12 11:30, Jim Klimov wrote:

However for smaller servers, such as home NASes which have
about one user overall, pre-reading and caching files even
for a single use might be an objective per se - just to let
the hard-disks spin down. Say, if I sit down to watch a
movie from my NAS, it is likely that for 90 or 120 minutes
there will be no other IO initiated by me. The movie file
can be pre-read in a few seconds, and then most of the
storage system can go to sleep.

Isn't this just a more extreme case of prediction?
In addition to the file system knowing there will only
be one client reading 90-120 minutes of (HD?) video
that will fit in the memory of a small(er) server,
now the hard drive power management code also knows there
won't be another access for 90-120 minutes so it is OK
to spin down the hard drive(s).
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