I have vague memories of a case from a long time ago, where an attacker had put some sort of data encryption in place with the key only in memory. Assuming that memory isn't from a fever dream...

1) While the system was up and running, data could be copied to/from the server in unencrypted form.
2) Pulling the plug meant losing access to the data, because it meant losing the encryption key to the on-disk information.

vSphere is not too expensive:
- Free licences for ESXi's basic functionality have been available for several years.
- vSphere 5.1 Essentials costs $500 and gives you licences for a basic vCenter and three hosts with two sockets each.