Hi David and Wanda,
We're planning to use another data mover on each ESX cluster to backup the data 
mover that does the snapshots. The main advantage we see is that the restore 
would be simple, and it is unlikely we would restore single files to it -which 
using a regular client backup would provide.  The downside is having to create 
and maintain 12 new data movers whose only job right now is to backup one small 
virtual machine each. The extra data movers  may get more work to do in the 
future if we split up cluster backups among more than one data mover. We didn't 
think very far or very deeply about this question, and may change solutions 
after more experience clarifies the merits of the alternatives.

Either should work, and it should be easy to switch. So my priority is to get a 
backup, any backup working.

Keith