[cisco-voip] Approximate service outage times for a 5.1->6.1 upgrade

[Kelemen Zoltan]

Hi,

I'm going to upgrade a cluster of two CUCM 5.1.2 servers (both MCS7845) 
from 5.1.2 to 6.1 release.

However, the customer is keen on knowing expected service outage times, 
and the duration of the whole operation in itself. Even if they do not 
expect exact timeframes, telling them "it will take a lot" just won't do :-)

So can anyone give me an idea, of how much time would it take to upgrade 
this cluster and of this, approximately how much would they be without 
service?

Especially, since, as far as I understand, upgrading in itself does not 
mean interruption is service, since I'm working on an inactive partition.

Also, is this planned order correct (basically based off SRND):
- upgrade first node, don't reboot
- upgrade second node (there's only one), don't reboot
- reboot first node with switching versions
- reboot second node with switching the version

the Feature licenses for the v6 should be uploaded before the upgrade 
process, or after the first node reboot?

thanks,
  Zoltan