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Re: Postgres on NAS/NFS

From: CS DBA <cs_dba(at)consistentstate(dot)com>
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: Postgres on NAS/NFS
Date: 2011-02-10 20:02:02
Message-ID: 4D54443A.3050600@consistentstate.com (view raw or flat)
Thread:
Lists: pgsql-admin
On 02/09/2011 03:49 PM, Jim Mlodgenski wrote:
> On Wed, Feb 9, 2011 at 2:59 PM, Bryan Keller<bryanck(at)gmail(dot)com>  wrote:
>> I am considering running a Postgres with the database hosted on a NAS via NFS. I have read a few things on the Web saying this is not recommended, as it will be slow and could potentially cause data corruption.
>>
>> My goal is to have the database on a shared filesystem so in case of server failure, I can start up a standby Postgres server and point it to the same database. I would rather not use a SAN as I have heard horror stories about managing them. Also they are extremely expensive. A DAS would be another option, but I'm not sure if a DAS can be connected to two servers for server failover purposes.
>>
>> Currently I am considering not using a shared filesystem and instead using replication between the two servers.
>>
>> I am wondering what solutions have others used for my active-passive Postgres failover scenario? Is a NAS still not a recommended approach? Will a DAS work? Or is replication the best approach?
> DAS will absolutely work. Just be careful to fence things properly so
> that you don't end up with 2 servers trying to start the data
> directory at the same time. It will lead to some pretty nasty
> corruption.
>
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Jim is right, be very careful to fence things properly.  Also, depending 
on how the NAS/DAS is mounted to the servers you may need to tweak 
permissions. I've seen NFS scenarios where the postgres user on the 
secondary machine has a different UID than the one on the source box and 
the result was a mount point owned by nobody:nobody which of course 
disallows postgres from accessing the file system.

-- 
---------------------------------------------
Kevin Kempter       -       Constent State
A PostgreSQL Professional Services Company
           www.consistentstate.com
---------------------------------------------


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