Re: archive falling behind

Hi I have reverted to cp as archive command, but know under heavy load (>
150 WAL segments in a minute) it happens that some wal segments gets
corrupted:

postgres(at)lemur:~/9.1/main/pg_xlog$ md5sum 000000010000001000000049
f1906d2745224430f811496df466203f 000000010000001000000049
postgres(at)lemur:~/9.1/main/pg_xlog$ md5sum
~/backups/wal/000000010000001000000049
7e73fe759e41e427497360a815f9d3e1
/var/lib/postgresql/backups/wal/000000010000001000000049

On Fri, Apr 26, 2013 at 10:55 AM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>wrote:

> German Becker wrote:
> > Here is the archive part of the config:
> >
> > archive_mode = on # allows archiving to be done
> > # (change requires restart)
> > archive_command = '/var/lib/postgresql/scripts/archive_copy.sh %p %f'
> # command to use to
> > archive a logfile segment
> > #archive_timeout = 0 # force a logfile segment switch after
> this
> > # number of seconds; 0 disables
>
> So the problem might be in that script.
>
> > The archive coommand makes a local copy and then it copies to the backup
> server via ssh. Both copies
> > are md5-checked and retried up to 3 times in case of failure.
>
> archive_command should not retry the operation, but rather
> return a non-zero return code.
>
> > I have seen under heavy load that some WALs are skipped, some have less
> size, some are corrupted (i,e,
> > the loop fails 3 times).
> > I'm not sure about the return value (checking it). What is the expected
> behaviour of the archiver?
> > Will it retry de archive if archive command returns differnt than 0?
> Will it retain the WAL segment
> > until it is succesfuly archived?
>
> See
> http://www.postgresql.org/docs/current/static/continuous-archiving.html#BACKUP-ARCHIVING-WAL
>
> archive_command should exit with zero only if the
> WAL segment was archived successfully.
> PostgreSQL will retry and retain the WAL segment until
> archival succeeds.
>
> Yours,
> Laurenz Albe
>