Re: [PERFORM] Backup taking long time !!!

Greetings,

* julyanto SUTANDANG (julyanto@equnix.co.id) wrote:
> Best practice in doing full backup is using RSYNC, but before you can copy
> the DATADIR, you might you pg_start_backup to tell the server not to write
> into the DATADIR, because you are copying that data. After finished copy
> all the data in DATADIR, you can ask server to continue flushing the data
> from logs, by commanding pg_stop_backup. Remember, not to copy the XLOG
> dir.

Whoah.  That is not, at all, correct, if I'm understanding what you're
suggesting.

PG most certainly *does* continue to write into the data directory even
after pg_start_backup() has been run.  You *must* use archive_command or
pg_receivexlog to capture all of the WAL during the backup to have a
consistent backup.

> There are another way more simpler, which is applying command
> pg_basebackup, which actually did that way in simpler version.

pg_basebackup has options to stream the WAL during the backup to capture
it, which is how it handles that.

> if you did pg_dump, you wont get the exact copy of your data, and you will
> take longer downtime to recover the backup data. By that way, recovering is
> only starting up the postgres with that copy.

pg_dump will generally take longer to do a restore, yes.  Recovering
from a backup does require that a recovery.conf exists with a
restore_command that PG can use to get the WAL files it needs, or that
all of the WAL from the backup is in pg_xlog/pg_wal.

Please do not claim that PG stops writing to the DATADIR or BASEDIR
after a pg_start_backup(), that is not correct and could lead to invalid
backups.

Thanks!

Stephen