HAMMER cleanup

[Thomas Nikolajsen]

When / how do we prefer to run HAMMER cleanup?

My thoughts:

It is important to cleanup HAMMER file systems regularly,
to get snapshots generated and prune & reblock so
file system doesn't get too fragment or fill up.

This should be done by default; this way users will
only get minimal extra administration tasks by using HAMMER.

Default action: `hammer cleanup';
with ability to specify other command.

command should, just like `hammer snapshot',
snapshot, prune & reblock all HAMMER file systems, including PFS.

 - periodic/daily
Executes in the night (starts 3:01 AM).
Cleanup by default; ability to disable (periodic.conf).
Fine for servers running 24h a day; not good for systems turned off at night.
Maybe periodic/monthly should also be used, so extended cleanup won't give disk trashing.

 - rc.d/hammer_cleanup
Executes at boot time.
Cleanup by default; ability to disable (rc.conf).
Fine for systems turned off at night.

I see no problem by enabling cleanup in both rc.d and periodic by default,
as `hammer cleanup' is a no op. if executed more than once a day.

If users want snapshot more often (eg. every hour), a cron script can do that,
this is very light weight to generate; normally it will normally be enough to
prune & reblock file system once a day.

I can make scripts for this, when we agree on what we want.

 -thomas