None of these are the gotchas cloud people seem to think they are. The answers look like this. Who's going to be on-call: the same people who are on call now.

None of these are the gotchas cloud people seem to think they are. The answers look like this. Who's going to be on-call: the same people who are on call now. HW failures don't need special on-call people. Who is going to build/manage your monitoring/alerting stack. Same people as now. Your servers are monitored, right? Adding RAID into the mix is hardly difficult. Will you hire a network engineer? No, colos will often offer to manage the network for you up to the switch and at that point it's just a matter of plugging the server in. You don't need any expertise to do that and remote hands can do it for you. Redundant hardware? Only if you need it currently. HW is reliable these days and you'd going to have spare capacity anyway, so this really doesn't change much. Disaster recovery? Take whatever answer you currently have in the cloud for multi-AZ.