My rule of thumb is pretty simple: if I see steal but still have an abundance of idle, I don't have a problem. If I see steal and low/no idle, I have a problem

My rule of thumb is pretty simple: if I see steal but still have an abundance of idle, I don't have a problem. If I see steal and low/no idle, I have a problem with an overcommited hypervisor. It's derived from stress testing and production across a variety of virtualisation platforms, and it's generally proven pretty accurate.