Tweaking Virtual Server Performance

Some architectural choices you can make in setting up your virtualization can improve your VM performance. Read the details in this KB, including:

• Use virtual SCSI hard disks instead of virtual IDE hard disks
  When you configure virtual machines, use virtual SCSI disks instead of virtual IDE hard disks. A virtual SCSI disk can make disk activity perform up to 20 percent better. A traditional IDE hard disk is limited to one transaction at a time on the bus. A SCSI disk can handle multiple transactions at the same time on the bus. Therefore, we recommend that you use SCSI virtual hard disks when you can.
• Use a fast hard disk subsystem in the host computer
  Like other disk-intensive programs, Virtual Server 2005 benefits from a fast hard disk subsystem on the physical server. Serial ATA (SATA) hard disks are faster than traditional IDE hard disks. Typically, SCSI hard disks are faster than both SATA and traditional IDE hard disks. The use of a striped RAID configuration provides even better performance and provides data redundancy. If you install Virtual Server 2005 in a storage area network (SAN) environment, and if you want to host virtual machines on a SAN, consider investing in host bus adaptors that have multiple fiber channels. With enough virtual machines and hard disk activity, you might saturate a fiber channel connection. To determine whether the fiber channel connection is saturated, monitor the performance of the fiber channel adaptor on the host computer.

Another great resource is the Virtual Server section of the ScriptCenter repository. There you can find gems like scripts to:

• Merge Virtual Machine Undo Disks
• Attach a DVD Image to all Virtual Machines
• Create a Virtual Network
• Modify Virtual Server DHCP Lease Times
• Search for a Virtual Server Security Entry