Re: Any experience using "shake" defragmenter? - Mailing list pgsql-performance

From Florian Weimer
Subject Re: Any experience using "shake" defragmenter?
Date
Msg-id 82k4hl81m0.fsf@mid.bfk.de
Whole thread Raw
In response to Re: Any experience using "shake" defragmenter?  ("Mark Felder" <feld@feld.me>)
List 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@bfk.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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