System Resource Costs of Hyper-V (Project Server 2007)
Costs associated with running a guest operating system on Hyper-V
As with any server virtualization software, there is a certain amount of overhead associated with running the virtualization code required to support guest operating systems running on Hyper-V The following sections summarize the overhead associated with specific resources when running guest operating systems on Hyper-V virtual machines:
The CPU overhead associated with running a guest operating system in a Hyper-V virtual machine ranges between 9 and 12 percent. For example, a guest operating system running on a Hyper-V virtual machine typically had available 88–91 percent of the CPU resources available to an equivalent operating system running on physical hardware.
The memory cost associated with running a guest operating system on a Hyper-V virtual machine is approximately 300 MB for the hypervisor, plus 32 MB for the first GB of RAM allocated to each virtual machine, plus another 8 MB for every additional GB of RAM allocated to each virtual machine.
Network latency directly attributable to running a guest operating system in a Hyper-V virtual machine is approximately less than one millisecond (ms), and the guest operating system typically maintains a network output queue length of less than one.
When using the pass-through disk feature in Hyper-V, disk I/O overhead associated with running a guest operating system in a Hyper-V virtual machine is found to range between 6 and 8 percent. For example, a guest operating system running on Hyper-V typically has available 92–94 percent of the disk I/O available to an equivalent operating system running on physical hardware.
Disk performance when running a Project Server 2007 solution on Hyper-V
Database performance is paramount to the overall performance of any Enterprise Project Management solution. Hyper-V introduces the concept of pass-through disks, which enable a physical disk or logical unit number (LUN) to be mapped directly and exclusively to a Hyper-V virtual machine. When using the pass-through feature, the NTFS file system on the root partition can be bypassed during disk operations, which minimizes CPU overhead and maximizes I/O performance. Hyper-V provides a synthetic SCSI controller and an IDE filter driver which both provide significant performance benefits over using an emulated IDE device such as is provided with Virtual Server 2005.
While both the SCSI controller and the IDE controller can be configured for pass-through operations, consider configuring pass-through disks for data volumes using the SCSI controller. This is recommended because the SCSI controller can only be installed if Hyper-V integration services are installed, whereas the IDE controller is available without installing Hyper-V integration services. If the IDE controller is installed without installing Hyper-V integration services, then disk I/O will be performed without the benefit of the IDE filter driver and will not be optimal. Therefore, to ensure optimal disk I/O performance for the data files in a Hyper-V virtualized environment, install integration services on both the host and guest operating systems and configure pass-through disks for data volumes with the SCSI controller.