A few clients have asked how we do capacity planning when estimating budget future growth (server purchases)?
Answer is simple: Call a psychic hot-line!
Or … use a simple formula to estimate demand. The two variables you need to know are:
Estimated Growth Rate of your VMs per year AND Consolidation Ratio
Formula: (Growth rate per year X Number of total VMs) ÷ Consolidation Ratio
Example: Company ABC has 300 VMs total with 20% growth per year. Their consolidation ratio is 10:1
So estimated needed hosts following year: (20% X 300) ÷ 10 = 6 hosts
Of course capacity planning goes far beyond a simple formula but this is just to give you a general idea. If you need to know when exactly you will need to purchase those additional hosts, then you need to do a bit more work to get data about your resource usage (a whole new topic). If you are doing a pre-virtualisation capacity planning then there is more meat on that bone. Perhaps will cover in greater detail in a later post.
Again, thank you for reading.