Re: Another WAL question

From: "Nick Fankhauser" <nickf(at)ontko(dot)com>
To: "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: "pgsql-admin" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Another WAL question
Date: 2001-09-12 17:53:41
Message-ID: NEBBLAAHGLEEPCGOBHDGIEINDKAA.nickf@ontko.com
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> In 7.1.3 and 7.2, there are only 2-3 WAL files kept because there is no
> need to keep them after a checkpoint.

This answers my original question- it sounds like after 3, they get recycled
or deleted, so if I reserve 48Mb (3*16) for these, I should be OK. ...Right?

> Is there any need to have these
> WAL config paramaters anymore?

I'd say all of the parameters you list below still make sense, as they all
control *how* the 2-3 WAL files are used. WAL_FILES might as well be 0-3
instead of 0-64, but I can still see an advantage to creating these in
advance to allocate the space.

> We currently have in postgresql.conf:
>
> #wal_buffers = 8 # min 4
> #wal_files = 0 # range 0-64
> #wal_sync_method = fsync # fsync or fdatasync or open_sync or
> open_datasync
> # Note: default wal_sync_method varies across platforms
> #wal_debug = 0 # range 0-16
> #commit_delay = 0 # range 0-100000
> #commit_siblings = 5 # range 1-1000
> #checkpoint_segments = 3 # in logfile segments (16MB each), min 1
> #checkpoint_timeout = 300 # in seconds, range 30-3600

Thanks for the good answers on this!

-Nick

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