Date: Tue, 8 May 2007 16:49:58 -0400 (EDT)
From: Charles Sprickman <spork@bway.net>
To: david@lang.hm
cc: =?UTF-8?B?5p2O5b2mIElhbiBMaQ==?= <liyan82@gmail.com>,
	PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Best OS for Postgres 8.2
In-Reply-To: <Pine.LNX.4.64.0705080043120.24680@asgard.lang.hm>
Message-ID: <Pine.OSX.4.64.0705081648060.392@hotlap.local>
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>
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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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