From: Alvaro Herrera <alvherre@commandprompt.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: jd <jd@commandprompt.com>
Cc: Ben Chobot <bench@silentmedia.com>
Cc: Steve Crawford <scrawford@pinpointresearch.com>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: BBU Cache vs. spindles
Date: Fri, 29 Oct 2010 15:49:12 -0300
Message-ID: <1288377894-sup-2286@alvh.no-ip.org> (raw)
In-Reply-To: <4CC07291.8020601@2ndquadrant.com>
References: <201010211651.o9LGp9I28474@momjian.us>
<4CC07291.8020601@2ndquadrant.com>
Excerpts from Greg Smith's message of jue oct 21 14:04:17 -0300 2010:
> What I would like to do is beef up the documentation with some concrete
> examples of how to figure out if your cache and associated write path
> are working reliably or not. It should be possible to include "does
> this handle full page writes correctly?" in that test suite. Until we
> have something like that, I'm concerned that bugs in filesystem or
> controller handling may make full_page_writes unsafe even with a BBU,
> and we'd have no way for people to tell if that's true or not.
I think if you assume that there are bugs in the filesystem which you
need to protect against, you are already hosed. I imagine there must be
some filesystem bug that makes it safe to have full_page_writes=on, but
unsafe to have full_page_writes=off; but I'd probably discard those as a
rare minority and thus not worth worrying about.
I agree it would be worth testing though.
--
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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Cc: alvherre@commandprompt.com, greg@2ndquadrant.com, bruce@momjian.us, scott.marlowe@gmail.com, jd@commandprompt.com, bench@silentmedia.com, scrawford@pinpointresearch.com
Subject: Re: BBU Cache vs. spindles
In-Reply-To: <1288377894-sup-2286@alvh.no-ip.org>
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