Showing posts with label vmware vcpu best practices. Show all posts
Showing posts with label vmware vcpu best practices. Show all posts

Friday 20 January 2017

Increasing/reducing RAM and CPU capacity of a VM after taking snapshot.

Or, is it possible to increase RAM/CPU capacity of a VM after taking snapshot?
Or, is it possible to reduce RAM/CPU capacity of a VM after taking snapshot?

Descriptions: If wondering whether CPU/RAM capacity of a virtual machine can be increased/reduced or not, the answer is Yes. You can reduce or increase the Memory as well as CPU capacity of a VM even after taking snapshot of the VM.

Logically, when you take snapshot of the Virtual Machine, the CPU and Memory state of the Virtual Machine get preserved. Means, no matter whether you want to increase or decrease the CPU/RAM capacity of the VM, whenever you will revert the snapshot the earlier configurations and status will be restored.

Test Case: When I tested this concept in my lab environment, I found that I am able to change the CPU and RAM configurations (increase or decrease) after taking snapshot of the Virtual Machine. When reverting the snapshot, the original status of the Virtual Machine is enforced.

No, No, No, you can’t increase or decrease drive capacity of any Virtual Machine after taking snapshot. J


Cheers, Please write me back if you have any query or feedback.

Saturday 20 February 2016

How to choose right number of Virtual Sockets and Core per Socket for a Virtual machine in VMware?

Or, What are the factors to consider while allocating CPU cores to a Virtual Machine?
Or, CPU Core allocation for a Virtual Machine in VMware vSphere.

Factors that should be considers while allocating CPU cores to a Virtual Machine:

On Virtual Machine:
1. Number of virtual sockets
2. Number of cores per socket












On ESXi Host:
1. Processor Sockets
2. Processor Cores per Socket
3. Logical Processors









Descriptions:
The truth is, you can choose to have any number of Processor Socket and Core per Socket while allocating vCPUs to any Virtual Machine. That’s the real virtualization concept. No matter how much processor socket your ESXi host have, or how much processor cores are mentioned per socket.
The only thing is, Number of CPU cores should match your requirement.
Example: If you want to allocate 6 vCPU (Cores) to a virtual machine, you can do it one of way shown below (both are correct):







Another thing that we should focus on is total number of Logical Processors (per host).
Logical Processor (host): This shows that, how much maximum cores can be allocated to a virtual machine if you want to keep one ESXi reserved for any specific virtual machine. If the total numbers of Logical Processors are 40, you can allocate 40 cores to a VM.

Please Note: It does not mean that you can’t allocate more than 40 Cores to a VM. But the good practice is to not overload the ESXi host. If you will overload it, its going to reduce the performance of the VM.

Overall allocation can go beyond 40 cores combining all/multiple VMs running on a ESXi host but the allocation for a single VM should not exceed the maximum capacity of it’s current host. In short, VMs can share their resources between VMs as per the usage and requirements, but Hosts can’t share resources with another Host in the cluster.

Example: lets understand what’s good and what’s not with the help of below graph.







Hope it will make your understanding clear about CPU allocation in VMware virtualization. For any feedback, suggestion or query, please write me back in comment box... above explanation is based my understanding of resources allocation. It may be changed or updated.


Cheers..!!