I've been playing with ESXi and Linux KVM to try to find out which one best suits our needs. With both of these solutions I've run into the same situation. After a guest has been idle for some time (let's say a night), it's slow to respond. I've noticed this problem both on ESXi and KVM, the first SSH login in the morning is always extra slow, also, we have a HTTP API server running on one of the guests, and it always times out the first request in the morning.
After the machine 'wakes' up it's alright, in fact, the guests on KVM are performing really well, with near native I/O speeds.
At first I thought it might be related to overcomitted RAM, however, decreasing guest RAM didn't fix the problem.
I'm having trouble pinpointing the cause of this problem, and I can't really find anything on google either. Is there anything I can do to relieve this issue?