I can tell you on OVH, a basic level VPS (one for $5.00/mo) is not encrypted. If a customer is willing to spend $7.00/mo more for an additional partition, they will be able to have storage to encrypt the the Tor relay information at rest.
If ovh vps gives root, bypass the fee with: md(4) vnode > geli > mount.
Then again, if the iron isn't dipped in epoxy (not done), in your own secure datacenter (not extant), on trusted #OpenHW (not AMD / Intel / or any other to date), built in trusted #OpenFabs (non extant), running validated #OpenSW (non extant), in a voluntarist libertarian environment free from force, one's use case might be moot.