a while ago I published a blog post that is located here that talked about the concept that more vcpus don’t necessary mean more performance, due to ready time, cpu timing and various other things. Read more on the blog post above if you are looking for more information!
This client went live with there system and was experiencing some database time outs, some sluggishness for consumer reports and meter usage. nothing something you want to have happen…
I was able to convince the vendor to let me actually try to REDUCE the number of cpus from 8 to 4, if you recall last time, the server was at 16.3% rdy for barely any load, it moved up to 28.9% during some data migration testing. so, let’s see the results with the cpus reduced….
as you can see it’s not 2.64% ! amazing!!!
the VM was no longer having any performance issues, was generating reports over 4x faster, and had no hiccups or sluggishness about it!
less cpus = more work!
If you look at the picture you will notice there are 43 vms on this host… with 59 vcpus. running the math 59/16 = 3.6875, so the ratio is 3.6875 vcpus to 1 pcpus. The VM runs around 13% util with burst of 66%, we could drop it down to 2 cpus or 3 cpus for even better ratios, and even more performance to all vms, however, the vendor still wont let me 🙂
so there we have it, proof, more cpus, doesn’t always mean better performance, and can in some cases, hurt performance.
always remember to start with low vcpus and move up, it’ll make the VMadmins and the VMs happy!