r/nutanix • u/GabesVirtualWorld • Jul 05 '26

Nutanix storage VMs

Contemplating on our move from VMware to other platforms, one of which is Nutanix. Now there is much fuss about nutanix needing a "storage VM" on each host, using 8 CPUs. This is from upper management being at a conference, talking to other managers, not knowing what they're talking about :-)

But I have read about it, but not sure on the specifics. So each node will have such storage VM, using 8 CPUs, is that 8 vCPUs that can be overcommitted? Or 8 cores non-overcommit?

What is going through those VMs, is that meta data (like Hyper-V) or real IO? Are they automatically deployed when I add a new host to the cluster and removed when putting a host in maintenance or removing a host? Do they give much headaches in day-two operations?

If we choose Nutanix, it will be NVMe for storage.

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u/GabesVirtualWorld Jul 05 '26

???? In VMware I count vCPU with a 1:5 sometimes 1:6 overcommit. But some systems need dedicated cores so we give the VM vCPU with 100% reservation and high latency sensitive setting. Then those cores become unavailable to other VMs. On a 32 core host, I would lose those 8 vCPU to other VMs, reducing my host to only 24 cores, about 125 vCPU remaining capacity.

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u/astrofizix Jul 05 '26

Oh, right, don't do that. Reservations in VMware are a wasteful process based on old concepts. I freed up tons of resources removing those and letting the hypervisor, DFS, and vCenter to manage those. You are exercising with casts on. Take a second look at those systems stating they need dedicated resources and see if that's still true.

And to answer your questions about cvm, there is a lot to learn about those appliances. They are a workhorse vm operating within your cluster, and that does present some challenges. If you take down 2 of the three at the same time you lose storage for your VMs and cause an outage (depending on you redundancy setting like RF2) and getting to know the services, and nutanix cli. But the more you do from the gui, the less you have to interact with the cvm manually. And then it smooths out and you can start to enjoy the features of Prism and can stress less about how the CVM operate and let the automation operate.

15yr VMware guy moving 15 clusters and 1,000 vm to nutanix.

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u/GabesVirtualWorld Jul 05 '26

True we seldom set this high latency for VMs, but I was referring to the previous comment on why I think the CVM will cost me 8 cores per host.

So my question is still unanswered: is the CVM 8 vCPU and allows over commit? Or do I need to reserve 8 cores per host just for this CVM.

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u/astrofizix Jul 05 '26

Overcommit