Q:
What would need to go into an assessment tool for a virtualization initiative?
A:
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:
- BUDGET
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 serverfault.com.