[DRBD-user] Problem updating 8.3.16 to 8.4.10 -- actually problem while *downgrading* (no valid meta-data signature found)

Lars Ellenberg lars.ellenberg at linbit.com
Mon Sep 25 22:44:14 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Mon, Sep 25, 2017 at 01:25:34PM -0400, Digimer wrote:
> On 2017-09-25 07:28 AM, Lars Ellenberg wrote:
> > On Sat, Sep 23, 2017 at 11:32:42PM -0400, Digimer wrote:
> >> I tried updating an 8.3.19 DRBD install (on EL6.9), and when I tried to
> > 
> > 8.3.16 is the latest I know... typo I assume.
> 
> Yup, typo. Was late...
> 
> >> connect the updated node to the older node, I got this error:
> >>
> >> ==[ old node ]==

> >> Sep 23 23:13:47 an-a02n02 kernel: block drbd1: incompatible after-sb-0pri settings
> > 
> > You have incompatible "after-sb-0pri" settings.
> 
> I saw that, but the docs said the config was backwards compatible and
> the after-sb-0pri was left as default.

defaults for after split brain recovery procedures have been
"disconnect" for as long as I can remember.

The suggested setting promoted in various examples is discard zero changes,
as that is the only "safe" (non-destructive) setting we have there,
and improves behaviour in case we had a *potential* data divergence
(both nodes primary at some time, during a time period where they have
not been able to communicate, and both already bumped their data
generation uuids), but at least one did not actually change anything yet.

> >> ==[ updated node ]==
> > 
> >> Sep 23 23:13:47 an-a02n01 kernel: drbd r0: incompatible after-sb-0pri settings
> > 
> >> ====================
> >>
> >> The config is (from 'drbdadm dump'):
> >>
> >> ====
> >> # /etc/drbd.conf
> >> common {
> >>     protocol               C;
> >>     net {
> >>         allow-two-primaries;
> >>         after-sb-0pri    discard-zero-changes;
> > 
> > So it claims it does not like this setting,
> > respectively that the handshake expected that setting
> > to be identical on both nodes, but it was not.
> 
> Isn't this the default back in 8.3 days? I don't recall ever changing it...

disconnect != discard-zero-changes

I admit we could have put that into the log message (not just that it
differs, but what the currently visible settings are)

> > So if you intend to downgrade to 8.3 from 8.4,
> > while you still have the 8.4 tools installed,
> > do: "drbdadm down all; drbdadm apply-al all"
> > Only then downgrade.
> 
> Noted for the future. In this case, I recreated the MD and did a full
> resync.

Always an option ;-)

    Lars




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