How many vCPUs can I have?

MattSpeller

TL;DR 20

scottalanmiller

@MattSpeller said in How many VCPU’s can I have?:

TL;DR 20

You CAN have way more than that.

Obsolesce

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

Obsolesce

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

That said, Hyper-V will tell you that the percent of total system CPU resources given to a VM will be 100% if you allocate the same number of total threads you have to a VM.

scottalanmiller

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

scottalanmiller

In ESXi 5 the limitation would have been 20 vCPUs.

Obsolesce

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Lots of good stuff there.

scottalanmiller

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Yes, we know Hyper-V's limits, but how did you know that he has Hyper-V in the first place? I've done a text search and until you said it, it was never mentioned in the thread.

Obsolesce

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Yes, we know Hyper-V's limits, but how did you know that he has Hyper-V in the first place? I've done a text search and until you said it, it was never mentioned in the thread.

It's like Apple or Arch Linux... if someone is using it, they WILL tell you. That he didn't say he was, tells me he's using Hyper-V.

scottalanmiller

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Yes, we know Hyper-V's limits, but how did you know that he has Hyper-V in the first place? I've done a text search and until you said it, it was never mentioned in the thread.

It's like Apple or Arch Linux... if someone is using it, they WILL tell you. That he didn't say he was, tells me he's using Hyper-V.

So your hypothesis is that a lack of pertinent information means it is a Microsoft user?

Obsolesce

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Yes, we know Hyper-V's limits, but how did you know that he has Hyper-V in the first place? I've done a text search and until you said it, it was never mentioned in the thread.

It's like Apple or Arch Linux... if someone is using it, they WILL tell you. That he didn't say he was, tells me he's using Hyper-V.

So your hypothesis is that a lack of pertinent information means it is a Microsoft user?

Am I wrong?

scottalanmiller

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

@scottalanmiller said in How many VCPU’s can I have?:

@Obsolesce said in How many VCPU’s can I have?:

The maximum you CAN have is 240 vCPUs per VM, which is a limitation of Hyper-V Server 2016.

How did you determine that Hyper-V is involved?

https://docs.microsoft.com/en-us/windows-server/administration/performance-tuning/role/hyper-v-server/processor-performance

Yes, we know Hyper-V's limits, but how did you know that he has Hyper-V in the first place? I've done a text search and until you said it, it was never mentioned in the thread.

It's like Apple or Arch Linux... if someone is using it, they WILL tell you. That he didn't say he was, tells me he's using Hyper-V.

So your hypothesis is that a lack of pertinent information means it is a Microsoft user?

Am I wrong?

Just making sure that I understood you.

Although in these cases, I would say that VMware is just as likely.

marcinozga

My rule of the thumb is start with 1 vCPU if it's Linux vm, 2 vCPUs if it's Windows, unless you enjoy Windows updates or Antivirus scans taking hours to complete....

Obsolesce

@marcinozga said in How many VCPU’s can I have?:

My rule of the thumb is start with 1 vCPU if it's Linux vm, 2 vCPUs if it's Windows, unless you enjoy Windows updates or Antivirus scans taking hours to complete....

This is how I do it too. Unless it's something that does nothing 99.99999% of the time like a license server on Windows.

Joel

So our host is HyperV 2016 core.

So if this is a 20 thread processor, could I be assigning double the amount of vCPUs?

The reason I asked is because we did have high cpu usage on our app01 and sqlserver but after adding one additional vcpu this massively helped so I was thinking, should I just double what I’ve got in there already and I’ll be okay?

scottalanmiller

@Joel said in How many VCPU’s can I have?:

So if this is a 20 thread processor, could I be assigning double the amount of vCPUs?

If you assign less than ~18, you are just throwing performance away. The threads will be idle. So yes, assign more.

scottalanmiller

In a situation like this, I would not assign more than 19 vCPU across the workloads.

Joel

Thanks all for the feedback. Useful to know.

scottalanmiller

@Joel said in How many VCPU’s can I have?:

DC- 1
FS - 2
APP - 3
SQL - 4

Into...

DC - 1
FS - 2
APP - 10
SQL - 6

Is probably how I would do it. That's 19.

But check your SQL licensing, that might cost you a fortune to increase it even a little.

Obsolesce

@scottalanmiller said in How many VCPU’s can I have?:

@Joel said in How many VCPU’s can I have?:

DC- 1
FS - 2
APP - 3
SQL - 4

Into...

DC - 1
FS - 2
APP - 10
SQL - 6

Is probably how I would do it. That's 19.

But check your SQL licensing, that might cost you a fortune to increase it even a little.

Virtual MS SQL is 4, more than that costs more.