Exchange Server Virtualization Support Policy Summary

Microsoft released their Microsoft Support Policies and Recommendations for Exchange Servers in Hardware Virtualization Environments document this month. I reviewed the support document and summarized the salient facts here.
Exchange 2007 Virtualization

Host Requirements:

• A hypervisor virtualization solution that has been validated by the Windows Server Virtualization Validation Program
• Adequate storage space to accommodate the host OS and components, paging file, management software and crash recovery (dump) files
• Storage space must be allocated for Hyper-V temporary memory storage (BIN) files, equal to the amount of RAM allocated to each guest

Guest Requirements:

• Exchange 2007 SP1 (or later) deployed on Windows Server 2008
• Cannot have the Unified Messaging Role installed
• The total maximum number of virtual processors cannot exceed the twice the number of physical cores.Typically 2 virtual processors are required for each Exchange server guest, but use this as a baseline
• Large mailboxes (1GB and larger) require the use of Cluster Continuous Replication (CCR)
• CCR nodes must be hosted on separate physical host servers to provide true redundancy and high availability
• Mixing physical and virtual nodes is supported for CCR and SCC environments
• Exchange supported backups must be run from the guest
• Both legacy backups (using ESE streaming APIs) and Exchange-aware software-based VSS backups (Data Protection Manager) are supported
• VSS backups of the an Exchange guest is supported if the guest uses only VHDs (not pass-through disks)

Guest Storage Requirements:

• Supports fixed size VHDs, SCSI pass-through and iSCSI storage
• Storage must be dedicated to one guest machine. In other words, a pass-through disk must be dedicated to one, and only one, guest.
• Guest OS must use a minimum fixed-size VHD of 15GB plus the size of virtual RAM allocated to the guest
• VHD limit is 2,040GB (nearly 2TB) in Hyper-V
• Hub and Edge Transport servers require sufficient storage for message queues and log files
• Mailbox servers require sufficient storage for databases and log files
• iSCSI storage using an iSCSI initiator within the guest is supported. This offers greater portability, but decreased performance

Not Supported:

• Dynamically expanding VHDs are not supported
• Snapshots or differencing disks are not supported
• Virtualization high availability solutions, such as Hyper-V Quick Migrations, are not supported. Only Exchange aware HA solutions (SCC, LCR, CCR and SCR) are supported.
• VSS backups of the Exchange guest machine's pass-through disk from the host are not supported

Recommendations:

• Storage should be hosted on separate disk spindles from the guest's OS
• Use SCSI pass-through storage to host transport and mailbox databases and transaction logs
• When using iSCSI storage, configure the iSCSI Initiator on the host and present it as a pass-through disk to the guest
• Use dedicated NICs with jumbo frames and not bound to a Virtual Network Switch, Gigabyte Ethernet, and isolated networks for iSCSI storage

Exchange 2003 Virtualization

Host Requirements:

• The hardware virtualization software is Microsoft Virtual Server 2005 R2 or any later version of Microsoft Virtual Server

Guest Requirements:

• Exchange Server 2003 SP2 (or later)
• Microsoft Virtual Server 2005 R2 Virtual Machine Additions must be installed on the guest operating system
• Exchange Server 2003 is configured as a stand-alone server and not as part of a Windows failover cluster
• Each guest must have only one CPU

Guest Storage Requirements:

• The SCSI driver installed on the guest operating system is the Microsoft Virtual Machine PCI SCSI Controller driver
• The virtual hard disk Undo feature is not enabled for the Exchange virtual machine

Recommendations:

• Consider adding a dedicated virtual network adaptor for Exchange Server backups
• Create separate fixed-size VHDs for Exchange Server databases and log files and store them on separate physical drives on the host
• Exchange Server performance should be validated before production by using the Exchange Server 2003 Performance Tools
• Make sure that the host server is sized correctly to handle the number of virtual machines that you plan to deploy
• Use a storage solution that enables fast disk access
• Antivirus programs should be configured to not scan VHD files