VMware Cloud Community
MallocArray
Contributor
Contributor

Sanity Check - 3 Hosts/2CPU or 6 Hosts/1CPU

I have a current farm of 3 BL460c servers running ESXi4. Each server is pretty much full with 8x2GB RAM and I'm looking for some more. I hate to pull out a 2 GB stick to put in a 4 GB as the cost to increase becomes higher. I have 3 other servers just like it I could repurpose for ESXi that only have half of their memory slots full. I'm considering pulling the second processor out of each blade so I can use my 6 CPU license on all 6 hosts, rather than 3 hosts with dual CPU (quad core). Looking at utilization on the blades right now shows less than 1/4 CPU utilization but over 80% memory utilization.

Does this make sense to consider? I understand that this could result in more vMotion happening if CPU utilization does go up on one host, but then I would have more memory slots available and could start putting 4 GB in the empty slots so I'm not removing perfectly good 2 GB sticks.

Part 2 of this question, if this makes sense to do, is there any way to tell ESXi to only use one of the physical CPUs in the box so I don't need to physically take out the proc and heatsink? I've looked in the BIOS and all I can see is a way to disable half of the cores on each processor which isn't what I want to do. I can remove them physically, but I don't have the plates to cover the socket to keep dust out, so if I didn't have to, that would be great.

Reply
0 Kudos
3 Replies
DPike
Enthusiast
Enthusiast

Can it be done...yes. Does it make sense? Well that depends on a cost vs performance standpoint. I assume the option of adding licenses/memory isnt one due to cost. You are gonna take a perfomance hit either way, and if your Virtualized Datacenter is going to continue to grow, I would suggest investing the money now to grow the infrastructure properly, vs, hackjobing it and having to correct it in the future.

That said, there isnt really a way to limit the CPU in regards to not having the license see it without just removing it.

If it were me, I'd push for more host build identically and additional licenses to do it right. That being side, your option is a viable one, just not the best one.


_________________

Dustin Pike

VMware Certified Professional (VI3 & vSphere)

Virtual Blocks Blog

_________________ Dustin Pike VMware Certified Professional (VI3 & vSphere) Virtual Blocks Blog
Reply
0 Kudos
MallocArray
Contributor
Contributor

Can you explain more about the performance hit? Ultimately I'll keep the same number of processors going, just across more hosts. CPU utilization across all of my blades is extremely low, less than 5 Ghz or 10% of the entire cluster, but memory is above 60% regularly after my most recent upgrade. It isn't very cost effective to buy more CPU license for this, but since most of my slots are used by 2 GB sticks, if I put in a 4 GB, I am only increasing by 2 GB.

I also thought I would benefit from more hosts as that is more for my HA cluster to fail over to, and with Power Management I can keep several of them asleep until I really need them.

If in the future I needed more CPU power, then I would already have the processors to put into the existing blades and it would be just a license increase to get them going.

Reply
0 Kudos
DPike
Enthusiast
Enthusiast

VMs have to wait to access cores of the physical CPU. 1 vCPU VMs wait for one core to become available before they can process. Order is decided by share. By limiting the number of cores that are available, you increase the wait time in situations of CPU contention. 8 Cores allows more VMs to work simultaneously than 4 cores allow.


_________________

Dustin Pike

VMware Certified Professional (VI3 & vSphere)

Virtual Blocks Blog

_________________ Dustin Pike VMware Certified Professional (VI3 & vSphere) Virtual Blocks Blog
Reply
0 Kudos