Greetings, * Martín Fernández (fmartin91@xxxxxxxxx) wrote: > On Tue, Feb 19, 2019 at 1:37 PM Stephen Frost <sfrost@xxxxxxxxxxx> wrote: > > * Martín Fernández (fmartin91@xxxxxxxxx) wrote: > > > Thanks for information! I've refactor our migration scripts to follow > > the suggestions. > > > > Please don't top-post on these mailing lists. > > > > > One extra question that popped up. As long as we don't start the standby > > (after running rsync), we can always `rm -f $PGDATA_10` and promote the > > standby if necessary for failover right ? We also need to `mv` > > pg_control.old to pg_control in the old data directory. > > > > Not sure which standby we're talking about here, but in general, yes, as > > long as you haven't actually started the system after the > > pg_upgrade/rsync, you should be able to blow away the new cluster that > > pg_upgrade/rsync created and start the old cluster back up and promote > > it (if necessary) and use it. > > > > Note that you should *not* need to do anything with pg_control, I have > > no idea what you're referring to there, but the old cluster should have > > the pg_control file and all the catalog tables in place from before the > > pg_upgrade/rsync (those aren't touched during the pg_upgrade/rsync > > process) and you would just need to start up the old binaries pointing > > at the old PG data directory and everything should just work. > > > I did some successful tests yesterday around this scenario. That standby in > this context is that one that received the rsync from the master but was > never started. The old data directory stays intact except for the fact that > globa/pg_control was renmaed with a .old > > I have found the documentation on pg_ugprade that states this: > > ` If you ran pg_upgrade without --link or did not start the new server, the > old cluster was not modified except that, if linking started, a .old suffix > was appended to > $PGDATA/global/pg_control. To reuse the old cluster, > possibly remove the .old suffix from $PGDATA/global/pg_control; you can > then restart the old cluster.` Ah, right, I forgot that it did that, fair enough. I've never been thrilled with that particular approach due to the inherent risks of people messing directly with files like pg_control, but that's how it is for now. Thanks! Stephen
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