Download Virtual Server 2005 – IDE to SCSI Virtual Machine Migration White Paper
This whitepaper describes tips and methods to help you migrate your Microsoft Virtual Server 2005 virtual machine from IDE to SCSI bus. You can increase overall virtual machine performance in most scenarios up to 20% by using SCSI virtual hard disks instead of IDE.
When you install Windows operating system, the setup procedure only installs the drivers necessary to the computer operation. In other words, it will install only the drivers for the devices the computer that are installed at that time.
Because of this, virtual machines that were installed using the default IDE bus lack SCSI support and simply changing the virtual disk drive bus to SCSI will not work. If you change the bus in an “unprepared” virtual machine, your next boot will fail with a stop error.