From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: James Cloos <cloos@jhcloos.com>
Cc: pgsql-admin <pgsql-admin@postgresql.org>
Cc: Lou Picciano <loupicciano@comcast.net>
Cc: jd@commandprompt.com
Subject: Re: binary logs: a location other than pg_xlog??
Date: Mon, 22 Nov 2010 14:25:41 -0500
Message-ID: <14940.1290453941@sss.pgh.pa.us> (raw)
In-Reply-To: <4CEA69F30200002500037D0B@gw.wicourts.gov>
References: <1557390103.902044.1290397034758.JavaMail.root@sz0093a.westchester.pa.mail.comcast.net>
<4788.1290402707@sss.pgh.pa.us>
<4788.1290402707@sss.pgh.pa.us>
<m3vd3p2o9l.fsf@jhcloos.com>
<4CEA69F30200002500037D0B@gw.wicourts.gov>
"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> James Cloos <cloos@jhcloos.com> wrote:
>> I notice that everyone suggests using a symlink, but I never see
>> anyone suggest just mounting a filesystem there.
> I think initdb wants an empty directory. Once it creates the
> directory structure with pg_xlog, if that's a mount point, it's a
> bit awkward to mount there and then copy from behind the mount point
> onto it. A symbolic link seems both safer and easier.
Well, either way you're going to have to modify things after initdb.
The notion of mounting a filesystem directly there scares me, on the
whole. Here is the problem: what if someday that filesystem happens not
to be mounted? Then you have a bare mountpoint directory, with no real
way for the postmaster to notice that that wasn't what you intended.
Hilarity ensues. (You might want to go back a few years in the archives
and read Joe Conway's report of what happened to his DB when a soft NFS
mount was a bit slow to mount one day. The symptoms for a missing
pg_xlog directory would be different but not better.) A symlink seems
to have a bit more error detection capability built in, especially if
you don't symlink to exactly the filesystem mount point but rather a
directory level or two down, so that the target dir is not there if the
mount fails.
regards, tom lane
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To: pgsql-admin@postgresql.org
Cc: tgl@sss.pgh.pa.us, Kevin.Grittner@wicourts.gov, cloos@jhcloos.com, loupicciano@comcast.net, jd@commandprompt.com
Subject: Re: binary logs: a location other than pg_xlog??
In-Reply-To: <14940.1290453941@sss.pgh.pa.us>
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