Just a local account. Before we would have to restart it manually every time there was a VM reset (over weekends, planned maintenance, etc). It would say the account PW was incorrect and we'd change it. Now we created a simple .bat file to hopefully automate this:
net stop ArcGIS Server
net start ArcGIS Server
and made a task scheduler item to run this.
It has the 0x2 error right now and am looking up the causes.