From: Scott Marlowe <scott.marlowe@gmail.com>
To: John Huttley <John@mib-infotech.co.nz>
Cc: pgsql-performance@postgresql.org
Subject: Re: Slow updates, poor IO
Date: Sat, 27 Sep 2008 16:54:20 -0600
Message-ID: <dcc563d10809271554wd20049ch5fee8f02b8a06d34@mail.gmail.com> (raw)
In-Reply-To: <48DEB4D4.1020100@mib-infotech.co.nz>
References: <48DBE587.3050406@mib-infotech.co.nz>
<20080926131556.GA1005@commandprompt.com>
<48DD6A4A.10209@mib-infotech.co.nz>
<dcc563d10809270809g17938b7fvf28a3624028e0f3b@mail.gmail.com>
<48DEB4D4.1020100@mib-infotech.co.nz>
On Sat, Sep 27, 2008 at 4:33 PM, John Huttley <John@mib-infotech.co.nz> wrote:
>
> > > this is part of the trade-offs of MVCC.
>
> > was... was a part of the trade-offs.
>
> You are thinking of HOT?
> I don't think it applies in the case of full table updates??
Sure, you just need a table with plenty of empty space in it, either
from vacuumed previous deletes / inserts or with a low fill factor
like 50%.
> It's really an effect of parallel updates / writes / accesses, and is
> always an issue for a database running on a poor storage subsystem. A
> db with a two drive mirror set is always going to be at a disadvantage
> to one running on a dozen or so drives in a RAID-10
>
> Oh well, I'm forever going to be disadvantaged.
Why? A decent caching raid controller and a set of 4 to 8 SATA drives
can make a world of difference and the cost is not that high for the
gain in performance. Even going to 4 drives in a software RAID-10 can
make a lot of difference in these situations, and that can be done
with spare machines and hard drives.
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To: pgsql-performance@postgresql.org
Cc: scott.marlowe@gmail.com, John@mib-infotech.co.nz
Subject: Re: Slow updates, poor IO
In-Reply-To: <dcc563d10809271554wd20049ch5fee8f02b8a06d34@mail.gmail.com>
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