Re: archived WALL files question

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От Frederiko Costa
Тема Re: archived WALL files question
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Msg-id 4BCC7804.9070604@gmail.com
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Ответ на Re: archived WALL files question  (Renato Oliveira <renato.oliveira@grant.co.uk>)
Ответы Re: archived WALL files question  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
Список pgsql-admin
Hi Renato,

I had the same question. I think, as far as I understood, the point is that if you have a few base backups, not only logs replay would be faster for a recovery but also you don't need to archive WAL segments before the base backup.

**
I also have a question regarding the frequency of log shipping  from the primary server to a directory exported to the standby server. The standby server is stopped ready to be launched in recovery mode. The point is in the primary server. I noticed the new logs files don't get copied to the directory specified on the archive_command. It's only copied when I do the pg_start_backup()/pg_stop_backup() base backup. Is this behaviour only achieved if I set archive_timeout? I did not want to do that, because I thought as soon as the 16MB WAL segment file got created it would be copied to the exported directory. Besides, I don't think I would need to perform base backups frequently.

Any advice?

Thanks

On 04/16/2010 12:00 AM, Renato Oliveira wrote:
I am sorry Kevin, I really appreciate your experience and your knowledge, and that's why I am asking; I thought the base backup was only necessary once. For example once you have done your first base backup, that is it, all you need is to replay the logs and backup the logs.

What would be the reason(s) for you to do weekly base backups?

Thank you very much

Best regards

Renato



Renato Oliveira
Systems Administrator
e-mail: renato.oliveira@grant.co.uk

Tel: +44 (0)1763 260811
Fax: +44 (0)1763 262410
http://www.grant.co.uk/

Grant Instruments (Cambridge) Ltd

Company registered in England, registration number 658133

Registered office address:
29 Station Road,
Shepreth,
CAMBS SG8 6GB
UK

-----Original Message-----


From: Kevin Grittner [mailto:Kevin.Grittner@wicourts.gov]
Sent: 15 April 2010 17:02
To: Renato Oliveira; pgsql-admin@postgresql.org
Subject: Re: [ADMIN] archived WALL files question

Renato Oliveira <renato.oliveira@grant.co.uk> wrote:
 
I was reading again the documentation... "The archive command
should generally de designed to refuse to overwrite any
pre-existing archive file."  This means it will keep writing logs
to the folder specified forever, and without an intervention, the
media will run out of space.   
Overwriting an existing file wouldn't help with that, since the
filenames keep changing.  It might, for example, prevent
accidentally wiping out the WAL files from one database cluster with
WAL files from another by copying the postgresql.conf file and
neglecting to change the archive script.
 
What do you guys do with regards to this situation, for example:
How to you clean up the old archived logs?   
We keep two weekly base backups and all the WAL files needed to
recover from the earlier of the two to present.  We also keep an
archival copy of the first base backup of each month with just the
WAL files needed to start it.  We delete WAL files when no longer
needed to support this retention policy.  It's all pretty automatic
based on bash scripts run from cron jobs.

Of course, you'll want to tailor your strategy to your business
needs.

-Kevin



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