Dec 09, 2011

What is the best method for virtual environment capacity planning?

The shared infrastucture of a virtual environment makes it a lot harder for me to plan capacity for than it is with a traditional server environment. The idea of virtualization is to efficiently use all of your resources, and this central concept is defeated if resources are unbalanced on a host. Too little physical memory causes VMs to start making up for it by switching to disks, then performance goes down the tubes. I've tried to look at resource trends historically to try to determine the balance point, while maintaining sufficient spare resource capacity to handle VMs when host failures occur. Basically, I feel like I am back in statistics class scratching my head and not only not knowing the answer, but being confused on how to get there. It gets complicated when I start trying to account for spare capacity as I plan capacity that meets future growth needs. In the end, I still feel like I am just making a slightly educated guess. Have suggestions for any useful tools that can help make capacity planning more meaningful than my current manual process?


Yep, attempting to plan capacity manually can be frustrating.  There are a number of tools out there that can help you, but they have one obvious downside; up front cost.  You will probably need to be able to use the ROI to justify the expense if you are not the one that signs the check, but as you clearly recognize, inaccurate capacity planning can create bottleneck and have a negative functional impact in a virtual environment.  There are two sources of virtualization managers that I can think off off the top of my head that might be able to help - OpTier and SolarWinds.  I am more familiar with OpTier BTM, which is very good, but they are really focused on large business focused in areas like telecommunications, production, finance and the like.  SolarWinds offers a virtualization manager that can automate the process and could possibly meet your needs, but I haven't personally used it.  Whatever product you decide on, an automated process will be a lot easier and probably more accurate than your manual attempts at capacity planning, unless you happen to be very good at it and spend a lot of time to get it done right.  

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