Do VMs reserve their cpu and memory? Or is it sharing?

[RahulKMNair]

Hi,

Suppose I have 10 core (10 X 2GHz) CPU. I want to create multiple 1 core VMs and the organization is using 'pay as you go model'. So how many VMs I can create here using vcd?

[npadmani]

Do VMs reserve their cpu and memory? Or is it sharing?'

Reservation of CPU or Memory by default in all the VMs would remain 0. and CPU and Memory share will remain Normal. so yes, it would be equal share. (allocation of resource would differ based upon need, and Shares are always proposal to that)

vSphere Resouce management guide would help you further more to understand this.

this same guide will also help you to understand how to reserve resources in terms of CPU and Memory for a VM.

Suppose I have 10 core (10 X 2GHz) CPU. I want to create multiple 1 core VMs and the organization is using 'pay as you go model'. So how many VMs I can create here using vcd?

This depends upon type of workload you are planning to run, let's say it's going to be Server workload, and you have decided to go with 6 vCPUs per Physical Core in your systems, than math on paper would be telling you that each VM with 1 vCPU assuming that they all have relatively moderate demand of CPU resources, then upto 60 VMs would be ok.

[RahulKMNair]

Thank you for the explanation!

I have a workload having 6 core CPUs in it and hyper threading is enabled as well. Total vCPU will be 12. I have created 3 vms with 4 vCPUs each. The problem is that when I create more VMs, its throwing the error "Provide vDC CPU/Memory Capacity is being over-committed". So how do I provision more VMs?

[npadmani · Accepted solution]

I should have paid more attention towards your question earlier, which clearly I didn't.

so earlier post from me was very much generic reply.

now if we talk about your vCloud Director environment, in which you have Org VDC with pay as you go model.

check the configuration settings of that Org VDC, look into CPU resource Guarantee and Memory rescue guarantee.

those are the settings will tell you that when you deploy a vApp on top of this Org VDC, in that vApp, how much reservation will be taken per VM.

and if your current workload is consuming those resources already, you won't be able to deploy more vApps after that.

please have a look at Duncan Epping's following blog post

vCD - Allocation Models - Yellow Bricks

take a look at the Pay as you Go allocation model which will give you some detailed idea with examples.

[RahulKMNair]

The link was helpful. Thank you.