På tirsdag 12. september 2017 kl. 19:19:22, skrev Bruce Momjian < br...@momjian.us <mailto:br...@momjian.us>>: On Thu, Aug 3, 2017 at 11:37:32AM +0200, Michael Paquier wrote: > On Mon, Jul 31, 2017 at 6:13 PM, Robert Haas <robertmh...@gmail.com> wrote: > > On Fri, Jul 28, 2017 at 10:35 AM, Andreas Joseph Krogh > > <andr...@visena.com> wrote: > >> I'm reading https://www.postgresql.org/docs/10/static/pgupgrade.html to try > >> to understand how to upgrade standby-servers using pg_upgrade with pg10. > >> > >> The text in step 10 sais: > >> "You will not be running pg_upgrade on the standby servers, but rather > >> rsync", which to me sounds like rsync, in step 10-f, should be issued on the > >> standy servers. Is this the case? If so I don't understand how the standby's > >> data is upgraded and what "remote_dir" is. If rsync is supposed to be issued > >> on the primary then I think it should be explicitly mentioned, and step 10-f > >> should provide a clarer example with more detailed values for the > >> directory-structures involved. > >> > >> I really think section 10 needs improvement as I'm certainly not comfortable > >> upgrading standbys following the existing procedure. > > > > Yeah, I don't understand it either, and I have never been convinced > > that there's any safe way to do it other than recloning the standbys > > from the upgraded master. > > Here are my 2c on the matter. 10-f means that the upgraded node may > have generated WAL with wal_level = minimal, which, at least it seems > to me, that we have a risk of having inconsistent data pages if only a > rsync is used on the old standbys. Like Robert, the flow we used in > the products I work on is to re-create standbys from scratch after the > upgrade using a fresh backup, with a VM cloning. An upgrade here is an > in-place process not only linked to Postgres, so standby VMs are made > of many services, some are being linked to Postgres. So this choice is > mainly decided by those dependencies, still it feels safer anyway.
I have applied the attached doc patch back to 9.5 to clarify pg_upgrade's rsync instructions and explain how it works. Improvements? Thanks, that certainly improves things. But; I still find the rsync-command in f) confusing; 1. Why --size-only? From rsync manual: "skip files that match in size", is this safe?? 2. Why is old_pgdata in the rsync-command, why is it needed to sync it? There are many ways to do/configure things it seems, resulting in many ifs and buts which makes section 10 rather confusing. I really think a complete example, with absolute paths, would be clarifying. I'm afraid many will still re-create standbys from scratch without a really good and complete example to follow. -- Andreas Joseph Krogh
