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How to determine the cores and RAM needed when converting a physical server into a VM?

mp flag

We are running a physical server that is not fully utilized. The task is to move this server to a VM. However, I am not sure how many cores and RAM to allocate to the VM. I know I can scale later, but my boss requires a cost estimate and I need as accurate an estimate as possible.

The server is running SAR, but I'm having a hard time coming up with an accurate estimate based on that.

So the question: What is the common way to determine how many cores and RAM a VM will need for the services (web server, database) to continue running smoothly in the new environment?

Nikita Kipriyanov avatar
za flag
Just observe/monitor how much resources are currently used on the bare metal and provide that much into the VM, adding something like 10% for virtualisation inefficiency and for spike usage?
mfinni avatar
cn flag
Except *don't* do that for CPU. If you're not CPU bound, or if you're not amazingly multi-threaded, don't overprovision vCPU cores. And consider running two VMs, one for the webserver and one for the database. Don't run them on the same OS instance.
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