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Re: DATA directory on network attached storage

From: Jeff Frost <jeff(at)frostconsultingllc(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: sfpug(at)postgresql(dot)org
Subject: Re: DATA directory on network attached storage
Date: 2005-04-08 17:11:07
Message-ID: Pine.LNX.4.62.0504081006590.11558@discord.dyndns.org (view raw or flat)
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Josh, thanks for the quick reply!

On Fri, 8 Apr 2005, Josh Berkus wrote:

> Jeff,
>
>>  Specifically is the performance of
>> gigE good enough to allow postgres to perform under load with an NFS
>> mounted DATA dir?  Are there other problems I haven't thought about?  Any
>> input would be greatly appreciated.
>
> The big problem with NFS-mounted data is that NFS is designed to be a lossy
> protocol; that is, sometimes bits get dropped and you just re-request the
> file.  This isn't a great idea with databases.

That is sort of what I was thinking, and we'll have to address this somehow.

>
> If we were talking SAN, then I don't see any reason why your plan wouldn't
> work.  However, what type of failure exactly are you guarding against?  How
> likely is a machine failure if its hard drives are external?

I believe we are looking to fulfill two possibilities.  First is failure, be 
it CPU fan, ram, motherboard, swap partition, kernel panic, etc.  Second is 
the ability to take the server offline for maintenance upgrades, etc.  A warm 
standby would be ideal to satisfy both conditions.  In the past we have done 
this with sloni, but sloni can be cumbersome when schema changes happen often 
on the db as is the case with this one.  pg-cluster is another option, but it 
appears it comes only as a patched version of postgres which would hamper our 
ability to change versions as quickly as might be desired.

Perhaps something shared could be done with PITR as this new install will be 
pg8.

-- 
Jeff Frost, Owner 	<jeff(at)frostconsultingllc(dot)com>
Frost Consulting, LLC 	http://www.frostconsultingllc.com/
Phone: 650-780-7908	FAX: 650-649-1954
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