Different versions of VxVM for one SSA

[Roy Alexander]

Is it possible and safe to manage one SSA with two different versions
of Volume Manager?

Here is my current setup:

   host_a
 -------------
 | OS 2.4    |
 |           |-------
 | VM 2.1.1  |      |    -------------
 -------------      |----| SSA 102   |
   host_b                |           |
 -------------      |----| FW 3.9    |
 | OS 2.4    |      |    -------------
 |           |-------
 | VM 2.1.1  |
 -------------

One host is active and the other is a hot standby. Only one 
host "owns" the SSA at a time by import/deport of the single 
disk group on the SSA. 

We are moving to a more fault tolerant setup with two new 
SSAs and each host connected to both SSAs. Since this system
is online 24x7, we must upgrade each host separately. As a 
first step, we plan to move to this setup:

   host_a
 -------------           -------------
 | OS 2.4    |           | SSA 102   |
 |           |-----------|           |
 | VM 2.1.1  |           | FW 3.9    |
 -------------           -------------

   host_b            
 -------------           -------------
 | OS 2.5.1  |-----------| SSA 112   |
 |           |           |           |
 | VM 2.3    |----       | FW 3.11   |
 -------------   |       -------------
                 |
                 |       -------------
                 |       | SSA 112   |
                 |-------|           |
                         | FW 3.11   |
                         -------------

The real question is could host_b with the newer OS and VM 
manage the old SSA 102 if some unforeseen problem arose with
the new SSA 112s AND host_a died (failover to host_b)?

If so, what would be required for host_b to "forget" the two SSA
112s and "learn" about the SSA 102?

We will run in this mixed configuration for a couple of days until
we are sure there are no problems with the new SSAs, OS, and VxVM.
During this evaluation period, I wanted to understand what my options 
were for this double fail scenario.

TIA,

Roy Alexander

________________________________________________________________________
 Roy Alexander |  "If you're going to write bad code,
 roya@iex.com  |   do it in someone else's language!"
 IEX Corp.     |   Bjarne Stroustrup -- creator of C++