| From: | Jon Nelson <jnelson+pgsql(at)jamponi(dot)net> |
|---|---|
| To: | Jim Nasby <jim(at)nasby(dot)net> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Davis <pgsql(at)j-davis(dot)com>, Florian Pflug <fgp(at)phlo(dot)org>, Andres Freund <andres(at)2ndquadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: corrupt pages detected by enabling checksums |
| Date: | 2013-05-13 00:41:26 |
| Message-ID: | CAKuK5J3UkB2tU_VUse1GFVwjANkLM_UO63V5j8dUJjwhcEOg6A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, May 12, 2013 at 3:46 PM, Jim Nasby <jim(at)nasby(dot)net> wrote:
> On 5/10/13 1:06 PM, Jeff Janes wrote:
>>
>> Of course the paranoid DBA could turn off restart_after_crash and do a
>> manual investigation on every crash, but in that case the database would
>> refuse to restart even in the case where it perfectly clear that all the
>> following WAL belongs to the recycled file and not the current file.
>
>
> Perhaps we should also allow for zeroing out WAL files before reuse (or just
> disable reuse). I know there's a performance hit there, but the reuse idea
> happened before we had bgWriter. Theoretically the overhead creating a new
> file would always fall to bgWriter and therefore not be a big deal.
For filesystems like btrfs, re-using a WAL file is suboptimal to
simply creating a new one and removing the old one when it's no longer
required. Using fallocate (or posix_fallocate) (I have a patch for
that!) to create a new one is - by my tests - 28 times faster than the
currently-used method.
--
Jon
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