Thread: More WAL archiving/backup questions

Hi once again

Am I right to assume that running a pg_dumo -Fc against a database:

(i) Does not require WAL log archiving be be switched on?
(ii) That running this will have no (or a very small) effect on the database's performance?

Also in general, are there any performance hits from runing in WAL Archiving mode and also any when a pg_start_backup is actually running

Thanks

Austen

Austen Birchall  Senior Database Administrator
Met Office FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884481 Fax: +44 (0)1392 885681
E-mail: austen.birchall@metoffice.gov.uk Website: http://www.metoffice.gov.uk

On Thu, May 12, 2011 at 02:29:41PM +0100, Birchall, Austen wrote:
> Hi once again
>
> Am I right to assume that running a pg_dumo -Fc against a database:
>
> (i) Does not require WAL log archiving be be switched on?

Correct.

> (ii) That running this will have no (or a very small) effect on the
> database's performance?

Not necessarily. pg_dump reads through all the data in every table, which can
certainly be a non-trivial IO load. Often people will direct pg_dump's output
to a file on the same filesystem as the database, which can certainly
overwhelm the disk. Sufficiently busy databases need to be careful about when
they backup.

> Also in general, are there any performance hits from runing in WAL
> Archiving mode and also any when a pg_start_backup is actually running

archive_mode being on or off probably doesn't make loads of performance
difference. pg_start_backup() causes a checkpoint, which can be IO intensive.

--
Joshua Tolley / eggyknap
End Point Corporation
http://www.endpoint.com