From: Stephen Frost <sfrost@snowman.net>
To: julyanto SUTANDANG <julyanto@equnix.co.id>
Cc: Dinesh Chandra 12108 <Dinesh.Chandra@cyient.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Backup taking long time !!!
Date: Sun, 22 Jan 2017 09:55:11 -0500
Message-ID: <20170122145511.GD18360@tamriel.snowman.net> (raw)
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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
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To: pgsql-performance@postgresql.org
Cc: sfrost@snowman.net, julyanto@equnix.co.id, Dinesh.Chandra@cyient.com
Subject: Re: Backup taking long time !!!
In-Reply-To: <20170122145511.GD18360@tamriel.snowman.net>
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