Advice on VMWare Hosts

[Sephiroth]

Hi,

 

I'm looking to upgrade my VMWare hosts and am looking at a couple of options, which I'd appreciate a second (or more!) opionin on.

 

We currently have 3 hosts with 2 x 16 core AMD Opteron processors and 64GB RAM connected to a vCenter server licenced for 6 CPUs, serving ~30 VMs.

 

What I'm looking at doing is to replace these with 4 single CPU servers with 192GB RAM. Firstly, would this be acceptable within the licencing? I've only ever seen dual processor hosts on the licence model we have.

 

Secondly, would dropping a processor in favour of 1 powerful one be recommended (based on our stats at the moment being ~5-10% CPU utilisation and ~90% RAM utilisation accross the cluster)?

 

The second part of that is; would you consider refurb hosts, considering that the design is that 2 of 4 hosts would run everything if necessary?

 

Thanks

[Domino]

Basically you want to make sure you have enough physical CPU cores to issue to your VMs to avoid a high ready state. If you're far beyond that already it would explain your low utilization. the servers are having to swap too often to make good use of the resource.

 

You want at least 1 core per vCPU (+ room for expansion if needed) + 1 host. That way you can run normally in the event of a failure. With that in mind more hosts can be beneficial.

[Sephiroth]

That makes sense. My cluster's CPUs are as follows:

 

(vCPUs/vCores total)

vmhost2: 26/36

vmhost3: 28/58

vmhost1: 28/56

Totals: 82/150

 

Forgive my ignorance, but are you suggesting that I need more than 82 physical cores or more than 150 physical cores?

[Domino]

The answer is "maybe"

 

When you commit more virtual cores than you have physical, then the VMs must be scheduled to have time on the processor. VMware has a metric in the vm stats for this they call "CPU Ready" and it's a measure in ms of the time waiting to schedule the VM onto hardware. They recommend going through a rightsizing exercise once in a while to set the vm allocations to what you can the VMs actually using. More here on that: http://www.edugeek.net/forums/enterprise-software/185012-want-compare-my-esxi-ram-allocation-others.html

 

This can cause slowdown and contention, and cause major issues if real time processing is needed on the VM (bigger issue for voice or video distribution applications)

 

Of course, the flip side is if you don't require fast access to the CPUs then it may not be an issue for you. But keep in mind that adding say, another 4vCPU VM exacerbates the slowdown across the entire estate - not just itself. As the cluster now has to fit more vCPUs into the same amount of physical CPUs.

 

Make sense?

[Chris_]

I'd check your licensing before you decide to go for 4 hosts. The cheap licensing for Essentials/Essentials plus only covers 3 hosts. If you require more than 3 you need to go up to the Standard edition.

[PotNoodleTech]

I would most certainly go for refurbished servers the Refurbished PowerEdge R720XD I have are amazing value for money. I'd never buy new now.

[Sephiroth]

I'd check your licensing before you decide to go for 4 hosts. The cheap licensing for Essentials/Essentials plus only covers 3 hosts. If you require more than 3 you need to go up to the Standard edition.

 

You are indeed correct. We're on Essentials Plus, so can only have 3 hosts anyway, unless we upgrade to Standard.

 

 

I would most certainly go for refurbished servers the Refurbished PowerEdge R720XD I have are amazing value for money. I'd never buy new now.

 

This is kind of what I thought. However, it may be redundant if I can't have more than 3 hosts. I can't seem to get anything newer than Intel E5 V2 processors (Ivy Bridge) with a maximum of 12 cores, which is lower than what I need, even with 2 processors, based on what is currently allocated on our cluster.

 

Thank you all, I will have a rethink

[PotNoodleTech]

Try server source they do custom Dell R730XD with whatever processors etc you want apparently up to 2 x 18 core.

 

Server Source - Europe's Leading provider of Refurbished Dell PowerEdge and PowerVault servers

 

I swear by R730s, they're awesome. Admittedly mine are filled with SSDs but they absolutely fly.

[Sephiroth]

Try server source they do custom Dell R730XD with whatever processors etc you want apparently up to 2 x 18 core.

 

Server Source - Europe's Leading provider of Refurbished Dell PowerEdge and PowerVault servers

 

I swear by R730s, they're awesome. Admittedly mine are filled with SSDs but they absolutely fly.

 

I've got in touch!

 

I have spoken to them before, but nothing came of it. Looks more promising this time. It is good to have a recommendation though.

[mikkydoos]

If you're using Veeam too I'm pretty sure their licensing will only cover you for 3 hosts in total if using per socket licensing.

@Domino is absolutely correct. I would be looking at maximising the number of cores regardless of actual sockets.