On Thu, 19 Jun 2008, Akins, Brian wrote:
On 6/19/08 2:44 PM, "Niklas Edmundsson" <[EMAIL PROTECTED]> wrote:
Includes the submitted fixes for:
"FIX htcacheclean" - Since we use a script that looks at atime we
don't use htcacheclean. The fix looks sane though.
FWIW, we saw a nice increase in performance when we turned off atime... We
eject things from the cache via an htcacheclean-like script that first
ejects expired objects then trims based on expire time and size.
Hmm, I vaguely remember having had this discussion before :)
Anyway, we serve mainly big files, and thus don't get that many
requests/s. The mozilla mirror is the extreme case in serving small
files actually (a few MB), and even then we have no real trouble
filling a GigE with 5ish year old hardware (provided good enough disks
to use as cache, a couple of 10kRPM U160 SCSI drives is fine).
We use Linux+xfs, and it copes with atime updates rather well (I think
they buffer the updates and delay commit of atime updates to disk,
something any sane OS/filesystem combo should do).
One big plus is that using atime we don't accidentaly purge DVD isos
that people are currently downloading on slow connections, a problem
quite obvious with the only-update-lastaccess-on-request method.
The only real issue is cleaning when under high load and close to
disk-full, it seems to take ages and forever to traverse the
filesystem then.
Brian: I remember you talking about some in-house modifications using
DBM or something to track accesses to cached data and using it to find
candidates to remove. Care to share?
/Nikke
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Niklas Edmundsson, Admin @ {acc,hpc2n}.umu.se | [EMAIL PROTECTED]
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