Re: BUG #14236: pg_upgrade failed

On Fri, Jul 29, 2016 at 11:49 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> Any help will be highly appreciated, we're gonna do the real upgrade on
>> Production next week , so this is very urgent, thanks in advanced
>
> The documentation says:
>
> If you use link mode, the upgrade will be much faster (no file
> copying) and use less disk space, but you will not be able to access
> your old cluster once you start the new cluster after the upgrade.
>
> "You can't access" also means can't re-upgrade the cluster.

Which is why you need to be careful and take a backup of the old
cluster's PGDATA when you use --link. Then in case of upgrade failures
you can fallback to that easily. Using --link has the advantage of
speed, and it has also the advantage to minimize the error handling
when a disk gets full if that's a constraint in what you do, because
you don't need to have up to twice the amount of space required to
hold on a system the old and new cluster's data (tablespaces on the
new and old instances share the same base path, with a different
sub-folder).
--
Michael