fighting the lack of good ideas

assessment and capacity analysis and planning for virtualization initiatives


What would need to go into an assessment tool for a virtualization initiative?


Typical factors may include:

  • current CPU load per server
  • what’s running on each server
  • current hardware of each server
  • expected percentage increase in usage
  • OS usage – homogenous or heterogeneous
  • new hardware or re-use current hardware
  • storage needs
  • vendor for virtualization (VMware, Microsoft, Xen)

And don’t forget the all-important:


My experience is all related around VMware, but what I’ve seen and used in the past is the following:

  • look at all CPU utilizations currently
  • add those average and peak percentages in two separate columns
  • plan for ~10% overhead from your hypervisor of choice
  • for every 40% of ‘average’ or 80% of ‘peak’, use one server of the type you now consider “high-end” (ie, if you have a total of 687% of ‘peak’, you need 9 physical servers running your hypervisor of choice)

Other thoughts:

  • I like to plan for 1 full spare physical server per ~6, so that I can utilize Vmware’s Vmotion for migrating servers around
  • plan for buying/utilizing SAN storage of some form so your VMs can be moved to different physical servers easily

I originally answered this topic ~2 years ago on