I assume that you are talking about running a validator node on the live Sovrin network as a Steward. For test purposes, we run nodes all the time in small VMs.
For nodes on the Sovrin network, please refer to sections 5 and 7 of the Sovrin Trust Framework. At the current time, we do not use nearly all the disk storage space specified in this document, but believe that over time we will. Some stewards do not currently have a full 1 TB drive dedicated at this time, but they are encouraged to mount a drive that can be upgraded for the partition that contains the ledger.