[cisco-voip] advice on upgrading large CUCM cluster with CoW from 8.6 to 10.5

[Dave Goodwin]

Has anyone performed an upgrade of a large cluster that uses Clustering
over the WAN from 8.6 to 10.5 that can share any lessons learned with that
specific type of scenario? The cluster is already virtual, has 16 nodes,
and is spread across 3 geographic areas. There is already a standalone PLM
on the network that will be loaded with the licenses prior to the upgrade.
I am trying to decide whether to do a standard upgrade, or utilize PCD to
perform a Migration task.

For the standard upgrade, I know there are a handful of things that need to
be done to prepare, like installing the necessary COP files. After the
initial RU has been completed to 10.5, I know that I would feel the need to
backup/reimage/restore, because I want the new VMs to have the ext4
filesystem, utilize the proper NIC driver for 10.5, and have the new
partition sizing.

For a PCD Migration, I have had a few issues trying to use it in the past
for other tasks. It seems to have gotten incrementally better and less
fussy over the past year or more, but it can still be somewhat fragile. I
see in the latest version of PCD 11.0 that it supports the use of remote
SFTP servers for servers that are remote from the PCD running the task.
Assuming it works as advertised, that should take out the significant
performance issues that would happen without that feature. The appeal here
is I know the VMs made by PCD are freshly installed machines with all the
right 10.5 traits I mentioned above, with data imported from the source
cluster. I do would not have to worry about the time required (and chance
of missing one of the many steps) to do all the manual tasks on a 16 node
cluster.

Finally, since this is a megacluster with CoW on top of that, I am
sensitive to the issues that can happen with DB replication after an
upgrade where it can take many hours to complete. Is there a way, either
manually or via PCD, to speed that up? For example, I would like to
consider running 'utils dbreplication setprocess 40' after the 10.5
publisher is up and running. Would that be the best way to handle it, and
it will it affect replication setups that have already begun? Does the
server or any services need to be restarted after running it. And, does the
command only need to be run on the publisher, or must I run it on each node
after it comes up on 10.5?

Any experiences or opinions are welcome. Thanks in advance!

-Dave
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/cisco-voip/attachments/20151201/232462c8/attachment.html>