From: Charles Sprickman <spork@bway.net>
To: david@lang.hm
Cc: 李彦 Ian Li <liyan82@gmail.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Best OS for Postgres 8.2
Date: Tue, 8 May 2007 16:49:58 -0400 (EDT)
Message-ID: <Pine.OSX.4.64.0705081648060.392@hotlap.local> (raw)
In-Reply-To: <Pine.LNX.4.64.0705080043120.24680@asgard.lang.hm>
References: <1178574927.533849.90730@e51g2000hsg.googlegroups.com>
<B699315F-9D8D-40E7-9C42-DD0C9E7DEA4F@blighty.com>
<463FFF76.5070108@gmail.com>
<Pine.LNX.4.64.0705080043120.24680@asgard.lang.hm>
On Tue, 8 May 2007, david@lang.hm wrote:
> one issue with journaling filesystems, if you journal the data as well as the
> metadata you end up with a very reliable setup, however it means that all
> your data needs to be written twice, oncce to the journal, and once to the
> final location. the write to the journal can be slightly faster then a normal
> write to the final location (the journal is a sequential write to an existing
> file), however the need to write twice can effectivly cut your disk I/O
> bandwidth in half when doing heavy writes. worse, when you end up writing mor
> ethen will fit in the journal (128M is the max for ext3) the entire system
> then needs to stall while the journal gets cleared to make space for the
> additional writes.
>
> if you don't journal your data then you avoid the problems above, but in a
> crash you may find that you lost data, even though the filesystem is 'intact'
> according to fsck.
That sounds like an ad for FreeBSD and UFS2+Softupdates. :)
Metadata is as safe as it is in a journaling filesystem, but none of the
overhead of journaling.
Charles
> David Lang
>
>> Steve Atkins wrote:
>>>
>>> On May 7, 2007, at 2:55 PM, David Levy wrote:
>>>
>>> > Hi,
>>> > > I am about to order a new server for my Postgres cluster. I will
>>> > probably get a Dual Xeon Quad Core instead of my current Dual Xeon.
>>> > Which OS would you recommend to optimize Postgres behaviour (i/o
>>> > access, multithreading, etc) ?
>>> > > I am hesitating between Fedora Core 6, CentOS and Debian. Can anyone
>>> > help with this ?
>>>
>>> Well, all three you mention are much the same, just with a different
>>> badge on the box, as far as performance is concerned. They're all
>>> going to be a moderately recent Linux kernel, with your choice
>>> of filesystems, so any choice between them is going to be driven
>>> more by available staff and support or personal preference.
>>>
>>> I'd probably go CentOS 5 over Fedora just because Fedora doesn't
>>> get supported for very long - more of an issue with a dedicated
>>> database box with a long lifespan than your typical desktop or
>>> interchangeable webserver.
>>>
>>> I might also look at Solaris 10, though. I've yet to play with it much,
>>> but it
>>> seems nice, and I suspect it might manage 8 cores better than current
>>> Linux setups.
>>>
>>> Cheers,
>>> Steve
>>>
>>>
>>>
>>> ---------------------------(end of broadcast)---------------------------
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>>>
>>
>> Regards
>>
>> Ian
>>
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To: pgsql-performance@postgresql.org
Cc: spork@bway.net, david@lang.hm, liyan82@gmail.com
Subject: Re: Best OS for Postgres 8.2
In-Reply-To: <Pine.OSX.4.64.0705081648060.392@hotlap.local>
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