From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
Cc: | List pgsql-patches <pgsql-patches(at)postgresql(dot)org>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [PATCHES] Infrastructure changes for recovery |
Date: | 2008-09-29 15:24:08 |
Message-ID: | 12423.1222701848@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-patches |
Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Mon, 2008-09-29 at 10:13 -0400, Tom Lane wrote:
>> ... If we crash and restart, we'll have to get to the end
>> of this file before we start letting backends in; which might be further
>> than we actually got before the crash, but not too much further because
>> we already know the whole WAL file is available.
> Don't want to make it per file though. Big systems can whizz through WAL
> files very quickly, so we either make it a big number e.g. 255 files per
> xlogid, or we make it settable (and recorded in pg_control).
I think you are missing the point I made above. If you set the
okay-to-resume point N files ahead, and then the master stops generating
files so quickly, you've got a problem --- it might be a long time until
the slave starts letting backends in after a crash/restart.
Fetching a new WAL segment from the archive is expensive enough that an
additional write/fsync per cycle doesn't seem that big a problem to me.
There's almost certainly a few fsync-equivalents going on in the
filesystem to create and delete the retrieved segment files.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Simon Riggs | 2008-09-29 15:32:54 | Re: Fatal Errors |
Previous Message | Tom Lane | 2008-09-29 15:18:19 | Re: Fatal Errors |
From | Date | Subject | |
---|---|---|---|
Next Message | Simon Riggs | 2008-09-29 15:54:55 | Re: [PATCHES] Infrastructure changes for recovery |
Previous Message | Simon Riggs | 2008-09-29 15:06:44 | Re: [PATCHES] Infrastructure changes for recovery |