Last week Citrix made available the paper: XenDesktop 4.0 Planning Guide – Hosted VM-Based Resource Allocation. The paper which contains 5 pages covers resource allocation recommendations for users running Windows 7 or Windows XP virtual desktops.
First the paper recommends to classify between Light, Normal, Power and Heavy Users, and based on this classification and OS used provide guidelines for vCPU and Memory allocation per Virtual Desktop. Also estimated IOPS for each Virtual Desktop during steady state (which doesn’t include boot, logon and logoff) are provided. The paper makes this estimates based on peak usage and not average users, so that maximum performance for end-users is guaranteed.
- CPU Allocation
o Most virtual desktops should only be configured with a single vCPU. Most user-based applications are only single-threaded and will not benefit from a multiple CPU configuration.
o Many user applications do not require significant amounts of processing, which negates the need for more CPU power.
o By allocating multiple vCPUs for each virtual desktop, extra resources are required to switch requests across the different vCPUs.
- Memory Allocation
o Users should be granted the maximum amount of RAM instead of average
o Memory ballooning/overcommit/dynamic memory should be disabled as it creates a negative risk to the overall user experience.