With the release of Windows 2012R2 and with it Hyper-V 2012R2 many of you are probably wondering how to migrate your existing environments to 2012R2.
For the first time Microsoft has issued that migration (from 2012) can be achieved with zero downtime. Now while this is possible there are certain requirements to be able to achieve this.
There are basically three ways in wich you can migrate to Hyper-V 2012R2 so I’ll outline them for you.

The first is and easiest way is you can live migrate the VM’s to the new server. However live migration is only possible between VM’s using shared Storage. Now you can’t add a windows 2012R2 server to a 2012 cluster so the only way you can achieve this is if you’re using SMB share as your storage.

Pros:

• Extremely fast migration
• No downtime

Cons:

• requires you to be using SMB storage

The second option is to perform a shared nothing live migration. In this scenario all VM’s are basically replicated the new server and after replication they are “live migrated” in the background.

Pros:

• No downtime

Cons:

• Time consuming as all VM’s have to be replicated to new server.
• If using Block Level Replication, requires a new Lun for the new server, existing Lun can’t be connected concurrently to new and old servers running different version of hyper-v.
• If using block level shared storage (Iscsi, Fiber) each VM is temporarily going to require double the space during initial replication.

The third and final option is to perform a cluster migration. This option is of course only valid if you have a cluster and are moving to a new cluster.
You basically perform a copy cluster role operation using Windows failover clustering and run the wizard.

Pros:

• All Cluster resources and settings are transferred to new cluster.
• Does not require additional Luns, or space provisioning

Cons:

• Requires downtime of the VM’s while transferring the Lun to the new server.

These are the three options for migrating VM’s to a new server. There is also a fourth option where you could just manually copy (or export) all VM’s to the new server and then import them via Hyper-V manager, but that isn’t really a migration.

Hope this helps you understand the basics of how to migrate your VM’s to Windows Hyper-V 2012R2 and again we see the benefits of using SMB shares as Hyper-V storage.
Happy Migrating.