| From: | "Jeffrey W(dot) Baker" <jwbaker(at)acm(dot)org> |
|---|---|
| To: | Guy Thornley <guy(at)esphion(dot)com> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-performance(at)postgresql(dot)org, Steve Poe <spoe(at)sfnet(dot)cc>, Chris Browne <cbbrowne(at)acm(dot)org> |
| Subject: | Re: Read/Write block sizes |
| Date: | 2005-08-24 05:25:21 |
| Message-ID: | 1124861121.11270.1.camel@noodles |
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| Thread: | |
| Lists: | pgsql-performance |
On Wed, 2005-08-24 at 17:20 +1200, Guy Thornley wrote:
> As for the async IO, sure you might think 'oh async IO would be so cool!!'
> and I did, once, too. But then I sat down and _thought_ about it, and
> decided well, no, actually, theres _very_ few areas it could actually help,
> and in most cases it just make it easier to drive your box into lseek()
> induced IO collapse.
>
> Dont forget that already in postgres, you have a process per connection, and
> all the processes take care of their own I/O.
That's the problem. Instead you want 1 or 4 or 10 i/o slaves
coordinating the I/O of all the backends optimally. For instance, with
synchronous scanning.
-jwb
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