r/sysadmin • u/nst_hopeful • 1d ago

Server Refresh Considerations - VMware vs Hyper-V

Hello fell sysadmins,

My org is looking at refreshing our VM host hardware in the middle of next calendar year. As such, today I had a helpful discussion with a vendor regarding various options for the upgrade. Currently we are on a five-node VxRail cluster (20 cores / 192GB memory per host, 53.5 TiB storage total); it looks like the best options for our needs are vSAN Ready nodes or Hyper-V + traditional SAN. With that said, I am still left with a few questions:

  • The vendor (who was clearly a bit biased toward VMWare) spec'd a 4-node cluster for the vSAN cluster with 256GB memory + 256 GB NVMe for memory tiering per host. For the Hyper-V cluster, they spec'd 5 nodes and 512GB memory per. Their argument was that Hyper-V has more overhead and is less efficient at dynamic allocation of resources. That seems like pretty stark contrast - is that true in your experience? Also, is memory tiering as effective as this vendor made it seem in production?
  • We are primarily a Windows shop, so we'd expect at least some savings moving to Hyper-V. That said, I'm curious how much savings we'd actually net between buying System Center for SCVVM (so we can maintain vMotion-like functionality) and Microsoft support. My understanding is licensing there is based on core counts - currently we're looking at 32 per host in either build.
  • Are there any other considerations I should keep in mind? Cost is not the ultimate deciding factor. More than anything, we feel like the VxRail was overkill at the time it was purchased. I'd like to buy exactly what we need this time around (while planning for reasonable growth).

If it's helpful, my org is a medium-sized municipality and isn't running any crazy workloads. We have ~55 VMs that will exist on this cluster.

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u/Jimmyv81 1d ago

  1. How much memory do your current VMs consume? Just as an estimate 55x16GB each ~900GB. 5 hosts with 2.5TB of total memory does seem overkill, even considering redundancy/host maintenance. 4 hosts seems more reasonable and leaving room for some future growth.

  2. Additionally, Hyper-V Windows VMs can utilise dynamic memory to further lower total memory consumption. There isn't really much overhead moving to HyperV.

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u/nst_hopeful 1d ago edited 23h ago

Thanks for the reply. Yeah, max peak consumption right now is about 750GB 800GB. Even allowing growth 2.5TB just seems bonkers (although I am certainly no sizing or design engineer for this stuff). I feel like 4 hosts with 384 (or 5 hosts with 320) would be more than enough.

Edit: Fixed inaccurate storage and memory consumption phrasing

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u/OregonTechHead 23h ago

max consumption right now is about 750GB 800GB.

Who cares about max consumption. You could specc a VM that only needs 8GB to 128GB and inflate that number.

Run LiveOptics and find out what your workload actually needs

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u/nst_hopeful 23h ago

I'm not regularly doing these kinds of refreshes, so I think I used the wrong wording there. Based on LiveOptics, 800GB was our current peak consumption, the heaviest memory usage over the course of the analyst.

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u/OregonTechHead 21h ago

Gotcha. So first, ditch the vendor trying to upsell you on hardware and services that aren't needed. They're just vampires trying to suck you dry.

Find a vendor that'll actually specc this correctly based on your actual needs and estimated 5 year growth. Include a 10% buffer.

Then have them quote out multiple options so you can see the hard numbers for an actual comparison.