Re: Standby servers and incrementally updated backups

On Jun 25, 2007, at 3:40 PM, Simon Riggs wrote:

> On Mon, 2007-06-25 at 13:42 -0500, Erik Jones wrote:
>
>> It is my understanding that once a standby server has reached the
>> point where it is often waiting for wal files to replay, it is pretty
>> much caught up to the primary server, with the differences being in
>> whatever wal files are currently in queue to be archived by the
>> primary.
>
> Yes. You can tell by using
>
>   select pg_xlogfile_name(pg_current_xlog_location());
>
> to see what the current file on the Primary is.

Thanks for the tip.

>
>>  If I'm correct, then for large databases wherein it can
>> take hours to take a base backup, is there anything to be gained by
>> using incrementally updated backups?
>
> If you are certain there are parts of the database not touched at all
> between backups. The only real way to be sure is to take file level
> checksums, or you can trust file dates. Many backup solutions can do
> this for you.

Wait, um, what?  I'm still not clear on why you would want to run a
backup of an already caught up standby server.

Erik Jones

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erik@myemma.com
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