Upgrading from 9.0 to 9.1 with SSO 1

[fraxx]

I'm installing a couple of new servers (a cluster actually) in an existing SAN. The SAN already have four nodes previously attached, compromised of two clusters. One of the cluster nodes is the "SSO Master" and the other nodes are "SSO Slaves". Those are all at Bexec 9.0.
The Bexec licenses for the new servers are for 9.1, and obviously I don't want to install 9.0 on the new machines. I was not allowed to install 9.1 on the new nodes, the install wizard balked at the fact that the SSO Master was at 9.0.
Basically, any real gotchas with regards to upgrading the existing servers from 9.0 to 9.1? Should I upgrade the master first or the slaves?
Any pointers are appreciated.
/charles

 

[justin2000]

yep stop all the BE services on the secondary servers.
If you have BE cluster aware, also break this.

Upgrade the primary server first, then the secondary's 1 by 1.