Re: When it's really necessary to enable WAR archiving in case of low level backups?

On Sun, Jul 7, 2019 at 12:15 PM Thorsten Schöning <tschoening(at)am-soft(dot)de>
wrote:

> From my understanding, without actually archving WAL segments, the
> WAL would simply grow until archiving gets enabled, without any
> influence on if the backup is consistent or not.

This is true if you set archive_command to the empty string, or to a
command that returns a failure code (like the linux command 'false'). But
if you turn archive_mode to off, or if you use an archive_command that
always returns success despite not archiving (like the linux command
'true') then the WAL would not be retained but would be lost.

So you would have to go through a complex cycle of having it return success
without archiving, then just before the backup change it to return failure,
then change it to actually archive and return success, then once all needed
WAL is archived change once more to return success without archiving.

That is a lot of complexity. What does it get you? The normal way has the
archive happen at the same time as the base backup, and I guess that that
network traffic could delay the basebackup itself, which then means you
have to archive the WAL that was generated during that delay. That is
something, but it doesn't seem like much to justify the complexity.

Cheers,

Jeff