Re: pg_xlog on a hot_stanby slave

On Tue, Jun 16, 2015 at 6:55 PM, Xavier 12 <maniatux(at)gmail(dot)com> wrote:

> Hi everyone,
>
> Questions about pg_xlogs again...
> I have two Postgresql 9.1 servers in a master/slave stream replication
> (hot_standby).
>
> Psql01 (master) is backuped with Barman and pg_xlogs is correctly
> purged (archive_command is used).
>
> Hower, Psql02 (slave) has a huge pg_xlog (951 files, 15G for 7 days
> only, it keeps growing up until disk space is full). I have found
> documentation and tutorials, mailing list, but I don't know what is
> suitable for a Slave. Leads I've found :
>
> - checkpoints
> - archive_command
> - archive_cleanup
>
> Master postgresq.conf :
>
> [...]
> wal_level = 'hot_standby'
> archive_mode = on
> archive_command = 'rsync -az /var/lib/postgresql/9.1/main/pg_xlog/%f
> barman(at)nas(dot)lan:/data/pgbarman/psql01/incoming/%f'
> max_wal_senders = 5
> wal_keep_segments = 64
> autovacuum = on
>
> Slave postgresql.conf :
>
> [...]
> wal_level = minimal
> wal_keep_segments = 32
> hot_standby = on
>
> Slave recovery.conf :
>
> standby_mode = 'on'
> primary_conninfo = 'host=10.0.0.1 port=5400 user=postgres'
> trigger_file = '/var/lib/postgresql/9.1/triggersql'
> restore_command='cp /var/lib/postgresql/9.1/wal_archive/%f "%p"'
> archive_cleanup_command =
> '/usr/lib/postgresql/9.1/bin/pg_archivecleanup
> /var/lib/postgresql/9.1/wal_archive/ %r'
>
>
> How can I reduce the number of WAL files on the hot_stanby slave ?
>

If the number of WAL files in pg_xlog are growing, then you need to look at
why the files are not getting deleted.

Do you see master and standby in sync ? You can check that by getting the
current pg_xlog position in standby.

Regards,
Venkata Balaji N

Fujitsu Australia