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Home > Archive > PostgreSQL Administration > January 2006 > WAL log archive frequency
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WAL log archive frequency
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| Chris Jewell 2006-01-19, 7:24 am |
| Hi,
Further to my question on PITR, I have now implemented it :-) However,
I was wondering about the frequency of archiving the WAL. Does
postgresql wait until the current WAL file has reached 16MB before
calling the archive_command? The reason why I ask is that last night,
after doing the base backup, I noticed that a WAL file had been written
to my backup server. This morning, I added a primary key to a table but
noticed that nothing was written to the backup server. Should it have
been?
Is there any method of forcing a WAL segment to be archived at a given
frequency irrespective of whether or not it is a full 16MB? Our
database changes so infrequently at the moment that I'm worried that
these small changes may not be backed up regularly by the PITR system.
Thanks,
Chris
--
Chris Jewell, BSc(Hons), BVSc, MRCVS
Dept of Maths and Statistics
Fylde College
Lancaster University
Lancaster
Lancs
LA1 4YF
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| Tom Lane 2006-01-19, 11:24 am |
| Chris Jewell <c.jewell@lancaster.ac.uk> writes:
> Further to my question on PITR, I have now implemented it :-) However,
> I was wondering about the frequency of archiving the WAL. Does
> postgresql wait until the current WAL file has reached 16MB before
> calling the archive_command?
Yes. The assumption is the archive_command may be too stupid to deal
with archiving the same file more than once, and/or might have
performance issues with doing that, eg, if it's writing to tape or some
kind of write-once media.
You can do something like saving the newest-by-timestamp file in the
xlog directory every minute or whatever via a cron job. This ought to
be better integrated though ...
regards, tom lane
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