Installing Hyper-V 2012 on T420: "we couldn't create a new partition or locate an existing one"

Trying to install Hyper-V (bare metal hypervisor, not a role) on T420 with PERC H710, getting an error message:

"We couldn't create a new partition or locate an existing one. For more information, see the Setup log files."

(Don't even have a clue where to look for "Setup log files" - don't think the installer has a place to write them to.)

What am I doing wrong here?

The server came with a pre-partitioned RAID1 mirror on H710 (the rest of the drives - yet unconfigured); dual SD cards with the VMWare hypervisor (to be erased or left alone).

Thanks in advance for any ideas.