Hi there,
From my side, if you are able to seperate your backups.
I took a look at the BE 2010 SCL (
http://seer.entsupport.symantec.com/docs/329254.htm), and it doesn't appear that SBS 2008 R2 is supported as a media server installation with Hyper-V installed.
So...this is what I would recommend:
1. Use the other server as a media server for your backups. Connect the LTO3 drive to it, and load an OS on. Load all the agents you would need in order to back up the applications you run (SQL, Remote Agent for Windows Servers, AOFO, and the Hyper-V agent if you want to do GRT restores).
2. You then need to decide whether or not you want to back up your VMs completely, or just the data they contain. 2 sides to this: backing up your VMs will allow for faster DR recovery, as you would simply restore your VM from the last backup. The downside to this is that the LTO3 tape probably won't be big enough capacity-wise, meaning spanned tapes. The other consideration is to look at using your external disk. Run a backup of your VMs to the disk, and then run that data off to tape during the day with no impact on your VMs.
If you back up your data, consider creating a VM template of your servers. You would restore this, along with the System State of your various servers, and the data attached. The upside to this is faster data restores...the downside is slower recovery as you need to recreate VMs before restoring data!
3. What sort of backup strategy are you going to use? Full backups or incremental? If your data isn't too big, full will work.
Best bet is to also look at at the BE 2010 Admin Guide (
http://seer.entsupport.symantec.com/docs/338514.htm). It does a bit more explaining on the Agent for Hyper-V.
Post any further questions here...
Laters!