antipaucity

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.}}