I, like many, love the new Hyper-V in Server 2012. NIC teaming, concurrent live migration, SMB VM storage, and the all-new Replica. Replica solves a few problems, but it’s definitely not a panacea on it’s own.
There is lots of info on Hyper-V Replica out there, but a few points I wanted to make that are being skipped for those of us new to it. Most importantly: Replica does not do automatic failover.
Things Replica can do:
- Keep a copy of your VM on another server and storage, up to within 5-15 minutes of current.
- Allow you to do a manual, “planned failover” for planned maintenance of host. After maintenance, it’s only minutes of manually failing back.
Things Replica can’t do:
- Failover automatically before host server auto reboots, such as a monthly Windows Updates.
- Auto start the replicas if primary host or VM’s goes offline. All starts of replicas are manual.
Now there are surely ways to automate these limitations with PowerShell, and certainly with System Center Orchestrator. Example could be a PowerShell script that does a Planned Failover on all VM’s as a shutdown script on the host. Also you might be able to create a script on replica host that watches for replicas in disconnected state, and then starts up replicas. If you’ve researched or tried this, let us know in comments.
Also, something that tripped me up the first time. The Move command, which seamlessly move’s your VM to another host without downtime and without shared storage… is incompatible with Replica, but Replica has it’s own Move built in, called Planned Failover. Clicking Move will give you bad news that you have to shutdown first, but really should say “hey, you’re using Replica, why not use the Planned Failover?”