For my uses at Y!, jails were great: I was using them to setup test environments that were closer to production: each jail had software to match one of the machine types in production, but I didn&#x27;t need to get a whole bunch of machines that would mostly be idle.<p>As I was my own jailer, lack of resource limits wasn&#x27;t a real problem. I greatly benefited from the lack of performance penalties; everything ran at the same speed in or out of the jail.  I had one or two systems running in VMs and they were terrible: a) things were clearly slower, b) virtual disk provisioning is terrible, c) timekeeping  (hopefully things have gotten better since 2011)