[DRBD-user] migration strategy?

Miles Fidelman mfidelman at meetinghouse.net
Fri Nov 18 19:33:47 CET 2011


Florian,

Thanks!  Exactly what I was looking for.  A couple of follow-ups if I migth:

Florian Haas wrote:
> On 11/18/11 16:56, Miles Fidelman wrote:
>>
>> Any suggestions re. a sequence of operations that allows me to:
>> 1.  install latest versions of everything (Debian, DRBD, Xen, Pacemaker,
>> etc.) on the new nodes (easy)
>> 2.  replicate data volumes to the new nodes while the VMs continue to
>> run on the old nodes
>> 3.  migrate the VMs to the new nodes
>> 4.  decommission the old nodes
>>
>> - all with minimal downtime for the VMs, and minimal (or no) period
>> where I don't have a backup copy of the data?
> This is assuming you're running your existing Pacemaker cluster on
> Heartbeat.

Yup.
> How about:
>
> 1. Shut down one of the old nodes, have Pacemaker take over all cluster
> services to the other.
> 2. Bring up the first of the new nodes. Do not start cluster services yet.
> 3. Sync DRBD. DRBD 8.3. will happily talk to 8.0.14.
>
I'm assuming you're suggesting that I do this by:
- dropping the secondary on the old node
- adding a new secondary on the new node
- syncing

Which leaves an uncomfortably long period when there's only one 
definitive copy of the volumes (not horrible, as the underlying disks 
are RAIDed, but still).  Or are you suggesting something else?

For the future, what would be the sequence for using 3-node (stacked) 
setup for this kind of migration (i.e., going from 2 nodes to 3 nodes 
and then back to 2), and am I correct that this is not possible with 
DRBD 8.0.14?

Thanks Again,

Miles



-- 
In theory, there is no difference between theory and practice.
In<fnord>  practice, there is.   .... Yogi Berra




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