On 10/15/18 5:09 PM, Benoit Lobréau wrote:
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.
We have focused on archive_command because the performance is much
better because it can be parallelized.
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.
The --repo1-retention-archive-type and --repo1-retention-archive options
allow you do keep WAL for a smaller number of backups in order to save
space.
https://pgbackrest.org/configuration.html#section-repository/option-repo-retention-archive
So, for example:
[global]
repo1-retention-full=4
# The following option is the default but included for clarity
repo1-retention-archive-type=full
repo1-retention-archive=2
This configuration will retain 4 full backups but only keep PITR WAL for
2 of them, i.e. the WAL generated between backups. The WAL required to
make a backup consistent is always retained so the 2 older backups can
be played to consistency but no further.
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.
pgBackRest certainly works with Pacemaker/Corosync and Patroni.
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.
Recovering WAL out of the archive is safer than using slots. Since the
WAL is transferred over the network compressed it can also save a lot of
bandwidth.
Regards,
--
-David
david@xxxxxxxxxxxxx
