Exchange and Hyper-V Live Migration

pham0329

We're in the middle of an upgrade from 2007 to 2010. The initial plan was to have 2 physical servers, but now that MS supports Exchange 2010 SP1 on Hyper-V cluster, we're thinking about just virtualizing our 2010 deployment.

Initially, we were going to have multiple physical servers, but now, we're pondering on the thought of having just one HA vm for exchange. Are there any caveat with performing a Live Migration on an Exchange server?

Claymoore

Microsoft's support policy regarding virtualized Exchange 2010 servers recently changed. Be sure to read the blog post and the Best Practices whitepaper:
Announcing Enhanced Hardware Virtualization Support for Exchange 2010 - Exchange Team Blog - Site Home - TechNet Blogs
Download details: Best Practices for Virtualizing Exchange Server 2010 with Windows Server® 2008 R2 Hyper V?

Biggest changes are the UM role is now supported as a VM and you can combine DAGs with live migration. Previously, you could have either Exchange HA or VM HA - not both - but now you can virtualize a DAG member. If you are talking about virtualizing a single Exchange server, that has been supported since 2007.

The challenge is how you scale. Hyper-V can only give 4 processors to a guest VM, and Exchange mailbox servers are hungry for processors and RAM. Be sure to go through the Mailbox Server Role Requirements Calculator to be sure you are sizing your servers correctly. You may need to scale out, rather than up, and that can complicate the design by requiring more servers. Guest RAM shouldn't be an issue, but you might hit the limit of a virtual disk and either need to add more virtual disks and split up your DBs or move to Pass-Thru Disks (which only work with iSCSI on Hyper-V). Dynamic memory won't be much help because a mailbox server will eat all the RAM you give it, and although it will give that RAM up for other processes on the local box, it won't be available to other VMs.

Also keep in mind that virtualization is hardware high availability, not service high availability. You can live migrate an Exchange VM for a measure of reliability, but you will lose mail service when you have to perform maintenance on the Exchange server itself. Multiple servers in a DAGs and CAS arrays will provide you service high availability if that is your requirement.