| From: | Florian Weimer <fweimer(at)bfk(dot)de> |
|---|---|
| To: | "Mark Felder" <feld(at)feld(dot)me> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Any experience using "shake" defragmenter? |
| Date: | 2011-01-31 16:44:07 |
| Message-ID: | 82k4hl81m0.fsf@mid.bfk.de |
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| Lists: | pgsql-performance |
* Mark Felder:
> Why do you feel the need to defrag your *nix box?
Some file systems (such as XFS) read the whole extent list into RAM
when a file is opened. When the extend list is long due to
fragmentation, this can take a *long* time (in the order of minutes
with multi-gigabyte Oracle Berkeley DB files). This phenomenon is
less pronounced with PostgreSQL because it splits large relations into
one-gigabyte chunks, and it writes the files sequentally. But a small
effect is probably still there.
--
Florian Weimer <fweimer(at)bfk(dot)de>
BFK edv-consulting GmbH http://www.bfk.de/
Kriegsstraße 100 tel: +49-721-96201-1
D-76133 Karlsruhe fax: +49-721-96201-99
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