As I discussed last week, Microsoft has updated their guidance and support regarding hypervisor high availability and live migration technologies with Exchange 2010. This is welcome news for anyone looking to virtualize Exchange 2010 on vSphere, as it now allows you to take advantage of vMotion and HA on all Exchange servers, even those in a Database Availability Group (DAG).
Microsoft’s language on this change in support is causing a little bit of confusion on exactly what they do and do not support. See the following section below taken from the Exchange 2010 System Requirements page on TechNet (bolded emphasis mine):
Exchange server virtual machines, including Exchange Mailbox virtual machines that are part of a Database Availability Group (DAG), can be combined with host-based failover clustering and migration technology as long as the virtual machines are configured such that they will not save and restore state on disk when moved or taken offline. All failover activity must result in a cold start when the virtual machine is activated on the target node. All planned migration must either result in shut down and a cold start or an online migration that utilizes a technology such as Hyper-V live migration.
The bolded section seems to be the part that is confusing some people into thinking that some VMware features are not supported. But think about it for a second – does that description really sound like any VMware feature other than a simple Suspend? vMotion doesn’t save anything to disk during a migration and HA doesn’t save anything during a failure/restart of a VM. So what is Microsoft describing here?
Remember back when Hyper-V was released and Microsoft was touting a feature called Quick Migration to compete with VMware's vMotion? It was called Quick Migration and not Live Migration because the virtual machine was paused briefly and the state of the virtual machine was saved to disk during the migration. From the Quick Migration with Hyper-V (opens a .doc) whitepaper:
For a planned migration, quick migration saves the state of a running guest virtual machine (memory of original server to disk/shared storage), moves the storage connectivity from one physical server to another, and then restores the guest virtual machine onto the second server (disk/shared storage to memory on the new server).
It’s clear that the language in the TechNet article applies only to Hyper-V Quick Migration and not vMotion or even Hyper-V’s newer Live Migration feature. Microsoft probably felt they had a large enough installed base of Hyper-V RTM that clarifying this language was important.
Rumor has it that enough people are confused by this language that Microsoft is planning on clarifying it soon. At the end of the day this language doesn’t apply to those of us virtualizing Exchange 2010 on vSphere. Both HA and vMotion are now supported and that’s all that matters to us.