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Re: Moving database install to new SAN

From: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
To: Chris Hoover <revoohc(at)gmail(dot)com>
Cc: Andrzej Zawadzki <zawadaa(at)gmail(dot)com>, pgsql-admin(at)postgresql(dot)org
Subject: Re: Moving database install to new SAN
Date: 2007-09-20 18:16:06
Message-ID: 46F2B8E6.4010108@commandprompt.com (view raw or flat)
Thread:
Lists: pgsql-admin
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Chris Hoover wrote:
>>> 2. copy whole data directory over to new SAN
>> If database is big, then I think that is much faster to copy running
>> database
>> to new SAN.
>> Then stop postgres and rsync what was changed - but this will be probably
>> only a few files.
> 
> 
> 
> I believe if you do this, you will not get a function database in the end.
> There is a lot of data that is held in memory/buffers that may not be
> flushed to the disks.  You have no guarantee you will get this data with
> this method.

The method would work if they are willing to have an outage. Basically
you do an initial rsync of the large db...

Then you shut down the db.

And rsync again, which will be faster than doing a complete move with
shutdown.

The key here is, if you use this method... there is *zero* way around
shutting down the database before the second rsync.


Sincerely,

Joshua D. Drake


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