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Re: archived WALL files question

From: Frederiko Costa <frederiko(at)gmail(dot)com>
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: archived WALL files question
Date: 2010-04-19 15:34:28
Message-ID: (view raw, whole thread or download thread mbox)
Lists: 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?


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(dot)oliveira(at)grant(dot)co(dot)uk
> Tel: +44 (0)1763 260811
> Fax: +44 (0)1763 262410
> Grant Instruments (Cambridge) Ltd
> Company registered in England, registration number 658133
> Registered office address:
> 29 Station Road,
> Shepreth,
> UK
> -----Original Message-----
> From: Kevin Grittner [mailto:Kevin(dot)Grittner(at)wicourts(dot)gov]
> Sent: 15 April 2010 17:02
> To: Renato Oliveira;pgsql-admin(at)postgresql(dot)org
> Subject: Re: [ADMIN] archived WALL files question
> Renato Oliveira<renato(dot)oliveira(at)grant(dot)co(dot)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
> -----Original Message-----
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