Re: hanging for 30sec when checkpointing

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
Cc: "Goulet, Dick" <DGoulet(at)vicr(dot)com>, pgsql-admin(at)postgresql(dot)org
Subject: Re: hanging for 30sec when checkpointing
Date: 2004-02-10 01:16:19
Message-ID: 20457.1076375779@sss.pgh.pa.us
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"scott.marlowe" <scott(dot)marlowe(at)ihs(dot)com> writes:
> That said we have a really HUGE (~200 drive) IDE storage array my web /
> app server sits on top of. No clue if that thing will reliably work under
> a database, and I'm in no hurry to find out.

> But since the fsync on WAL is all that seems important, I could always
> initlocation a big chunk of it and keep the WAL local and I should be ok.

Unfortunately not --- at checkpoint time, the constraint goes the other
way. We have to be sure all the data file updates are down to disk
before we write a checkpoint record to the WAL log. So you can still
get screwed if the data-file drive lies about write completion.

regards, tom lane

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