[DRBD-user] Failing to migrate two DRBD nodes

Dan Barker dbarker at visioncomm.net
Wed Jan 12 16:02:07 CET 2011

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

I'm not sure why you say "makes the devices quite unusable", I'm wondering
why. Is your syncer speed set way too high? If you only allow syncer 20% of
your bandwidth, the impact should be nearly nothing. It might take more
clock time, but you wouldn't be in such a hurry.


-----Original Message-----
From: drbd-user-bounces at lists.linbit.com
[mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Marc Richter
Sent: Wednesday, January 12, 2011 7:26 AM
To: drbd-user at lists.linbit.com
Subject: [DRBD-user] Failing to migrate two DRBD nodes

Hi There.

I'm still failing in replacing a HA - node and home someone may help me.
I'm trying the following:
I have two nodes which serve as a HA - NAS and are connected by DRBD. We
have bought new Hardware and installed a new version of the Linux
Distribution onto this new devices. Since the complete initial sync takes a
long time and makes the devices quite unusable for 5 hours, I'm planing to
do the following:

1) Remove the secondary node from the cluster by issuing "drbdadm disconnect

2) Connecting the first new node to this removed node and have the initial
re sync done without affecting the live node.

3) When they have synced, disconnect these two nodes and re-connect the new
one to the still productive old one, to have the changes synced, which
occurred during the last few hours since the initial rebuild was running.

4) When they have synced, remove the old one from the cluster and have the
now synced new one serving all requests.

5) Connecting the second old node to the second new one and again let them
do the initial syncing.

6) After this is done, reconnect the second new node to the first.

7) I'm done with a very short downtime.

I previously set up 4 virtual machines (2 old ones, 2 new ones) which used
_exactly_ the same Versions of the OS, which the real nodes are running on
and copied the Configurations for drbd exactly from the real nodes (changed
only the IPs).
This way I could successfully finalize and simulate this plan. All went
well, so far.

Now I'm trying the same with the real nodes, but I'm stuck with point 3).
I've successfully synced the secondary old node with the first new one.
But when I try to connect this new node to the second (productive) old node,
I get the following in the Logs: "Unrelated data, aborting".
I googled for this, but don't understand what has/is happening here:

I extracted the UUID from the secondary old node (SyncSource) by issuing
"drbdadm show-gi r0" and got
This is exactly the same string I get when I issue the same command on the
SyncTarget (first new node I connected to this old one).
When I issue this on the currently productive old one I'm trying to connect
to, I get

As far as I understand all of this, drbd rejects to connect the two nodes,
because the UUIDs (the part
without the trailing state Bits) differ (correct?).

But how can this be? The sync source I used was connected to the other node
and the whole thing worked perfectly for a long time.
And what can I do now to connect these two nodes?
Can / should I change a part of the UUID - String on any of the nodes or
such? And if so, how?

Thanks very much in advance.

Best regards,
drbd-user mailing list
drbd-user at lists.linbit.com
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