From: Hannes Dorbath <light@theendofthetunnel.de>
Subject: Re: [GENERAL] Backup
Date: Wed, 06 Feb 2008 14:29:16 +0100
Organization: Hub.Org Networking Services
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To: Chander Ganesan <chander@otg-nc.com>
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In-Reply-To: <47A1E2F6.7060108@otg-nc.com>
To: pgsql-admin@postgresql.org

Chander Ganesan wrote:
> Magnus Hagander wrote:
>> On Thu, Jan 31, 2008 at 03:34:05PM +0100, Martijn van Oosterhout wrote:
>>  
>>> On Thu, Jan 31, 2008 at 01:28:48PM +0000, Simon Riggs wrote:
>>>    
>>>> That sentence has no place in any discussion about "backup" because the
>>>> risk is not just a few transactions, it is a corrupt and inconsistent
>>>> database from which both old and new data would be inaccessible.
>>>>       
>>> Hmm? I thought the whole point of a filesystem snapshot was that it's
>>> the same as if the system crashed. And I was fairly sure we could
>>> recover from that...
>>>     
>>
>> That was my assumption as well. *Assuming* that the filesystem 
>> snapshot is
>> consistent. There are a bunch of solutions that don't do consistent
>> snapshots between different partitions, so if your WAL or one 
>> tablespace is
>> on a different partition, you'll get corruption anyway... (seen this in
>> Big Commercial Database, so that's not a pg problem)
>>   
> Agreed.  That's why I made it a point to mention that all of your 
> tablespaces should be on the same file system...  In hindsight, I should 
> have also stated that your WAL logs should be on the same file system as 

One more reason to consider using Solaris ZFS -- it does consistent 
snapshots across all file systems.


-- 
Best regards,
Hannes Dorbath