By the way, do/can they both use streaming to receive WAL records? Or
streaming is only for standby servers. For backups you have only
file-based log shipping?
barman supports streaming but it's not as magical as one might think.
See pgbarman's documentation for how to manager .partial files.
pgbackrest archives only wal files when postgres uses the archive_command. You also have the option to do paralllel async wal push/get.
It can be useful if you write wals quicker than you can archive them or if you want to restore more quickly.
Then, I suppose they both don't support partial PITR
(http://docs.pgbarman.org/release/2.4/#scope), where there are
standalone backups that extends to points in time for which there are
no WAL files. I'm not sure if this matters, but I assume that it might
be effective in terms of disk space.
It's a hot backup so you have to have wals files so that your backup is consistent at the end of the backup.
You can build something like what you describe with pgbackrest, archive-copy and a copy of the backup directory to another place.
Like, base backups + WAL files covering the last month, and a couple
of standalone backups for a couple of months before that. Compared to
base backups + WAL files covering the same period of time.
I see. Yes keeping the wal for months can take some space...
By that you mean, why use repmgr, that targets specifically PostgreSQL
in place of Pacemaker + Corosync which are more general pieces of
software?
I'd like to be able to handle db failure as fast as possible. Ideally,
automatically. Which probably means either repmgr, or corosync +
pacemaker + PAF. Is that what you mean by HA here?
yes. You can also look into patrony for an alternative. It's a matter of preference and requirements.
Set up like corosync & pacemaker can be a little complex at first. But HA is not a trivial matter. And fencing is tricky to set up correctly.
If you require Hight availability it means you value your data and what your service up. So it's a non sense to go quick and cheap. You should try each and see for your self. (I contributed to PAF so I am not unbiased)
Or at least, have a
running instance I can switch to manually. Which means, for example,
pgBackRest's streaming replication.
I am not following here. switchover doesn't requiert a backup tool. For your switchover you just have to stop the master (so that all wal file are sent to online stanbies) and promote the standby.
If your standby is lagging too far behind (and you dont use slots) you can use pgbackrest's archive to fill the gap in wal files and catchup with the master.
regards,
Benoit
