From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
---|---|
To: | pgsql-patches(at)postgresql(dot)org |
Subject: | Re: Load distributed checkpoint V3 |
Date: | 2007-04-06 18:56:21 |
Message-ID: | Pine.GSO.4.64.0704061008590.13131@westnet.com |
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Lists: | pgsql-hackers pgsql-patches |
On Fri, 6 Apr 2007, Takayuki Tsunakawa wrote:
> Hmm... what makes you think that sync writes is useful for Oracle and
> not for PostgreSQL?
They do more to push checkpoint-time work in advance, batch writes up more
efficiently, and never let clients do the writing. All of which make for
a different type of checkpoint.
Like Simon points out, even if it were conceivable to mimic their design
it might not even be legally feasible. The point I was trying to make is
this: you've been saying that Oracle's writing technology has better
performance in this area, which is probably true, and suggesting the cause
of that was their using O_SYNC writes. I wanted to believe that and even
tested out a prototype. The reality here appears to be that their
checkpoints go smoother *despite* using the slower sync writes because
they're built their design around the limitations of that write method.
I suspect it would take a similar scale of redesign to move Postgres in
that direction; the issues you identified (the same ones I ran into) are
not so easy to resolve. You're certainly not going to move anybody in
that direction by throwing a random comment into a discussion on the
patches list about a feature useful *right now* in this area.
--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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