Many general VMSphere/Hypervisor Questions - from a VM noob

[Clarkington]

Hello,

I'm trying to wrap my head around the vm technology and I was hoping I could get some general pointers. Any assistance to my below questions would be most helpful.

1. What is the difference between Hypervisor ESXi and VMSphere?

2. Do I have to purchase hardware on the HCL to install the software?

3. I'm able to get a free license for VMware vSphere Hypervisor ESXi 4.1+ from the VM website. When I read the ESXi installation guide it mentions purchasing licenses and going from host to evaluation mode. What do this mean? Do I full functionality with the free license?

4. Is there any way to calculate RAM needed? The ESXi installation guide suggested that 4x Guest OSs requiring 512 MB RAM each would end up requiring 4 GB RAM in the physical hardware. Does anyone have a guide for calculating costs? Is there a fixed RAM overhead for the hypervisor software than then fixed amounts for each additional Guest OS that is actively running?

5. Can I run more than one Guest OS per core or processor? Should I allocate only one Guest OS per core or processor?

6. Here is the application I am looking to create - would the VMSphere be the correct software tool?

One physical set of hardware in a lab running several virtual machines which are different flavors of windows server. Our application will be loaded on each version of windows so we can check to see how the application reacts to different OSs. The traffic/impact on the server from our application is negligible.

If there is any clarification needed please let me know.

[Dave_Mishchenko · Accepted solution]

1. What is the difference between Hypervisor ESXi and VMSphere?

The ESXi Hypervisor edition refers to VMwares free licensed edition of ESXi.  vSphere refers to the paid version of ESXi.  It's the same code and the license key that you apply (whether it be free or paid) determines the features that are available.

2. Do I have to purchase hardware on the HCL to install the software?

No, but if you go with low end hardware you may end up with performance or stability issues that reflect the hardware choice.

3. I'm able to get a free license for VMware vSphere Hypervisor ESXi 4.1+. When I read the ESXi installation guide it mentions purchasing licenses and going from host to evaluation mode. What do this mean?

When you sign up for free ESXi you'll get a serial number.  Apply that the same way as documented in the install guide.

4. Is there any way to calculate RAM needed? The ESXi installation guide suggested that 4x Guest OSs requiring 512 MB RAM each would end up requiring 4 GB RAM in the physical hardware. Does anyone have a guide for calculating costs? Is there a fixed RAM overhead for the hypervisor software than then fixed amounts for each additional Guest OS that is actively running?

Allocate 2 GB for ESXi and overhead and then add what you need for VMs.  One of my tests hosts has 9 VMs allocated 13 GB and the host is reporting 14 GB in use.  ESXi is pretty good with sharing memory between VMs so you can over allocate memory, but ideally get as much as you can.  It'll make it easier if you find you're running more VMs that you planned for.

5. Can I run more than one Guest OS per core or processor? Should I allocate only one Guest OS per core or processor?

You can run more that one vCPU per core.  If the host is lightly loaded you may get between 5 and 8 vCPUs per core.  It really depends on your VM load.

6. Here is the application I am looking to create - would the VMSphere be the correct software tool?

One physical set of hardware in a lab running several virtual machines which are different flavors of windows server. Our application will be loaded on each version of windows so we can check to see how the application reacts to different OSs. The traffic/impact on the server from our application is negligible.

It'll be fine for that.

Dave
VMware Communities User Moderator

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[Clarkington]

Dave, all of your answers hit the nail right on the head. Thank you!

I had a couple follow up questions if you don't mind.

1. Comparing the free and paid Hypervisor and VMSphere - would you be able to tell me what I gain with the VMSphere?

2. Your answer regarding vCPUs - you state:

"You can run more that one vCPU per core.  If the host is lightly loaded you may get between 5 and 8 vCPUs per core.  It really depends on your VM load."

How would you support 5-8 vCPUs per core? Does it use CPUs in an on-demand fashion? i.e. you have 4 Guest OS systems that require 2.0 GHz CPUs each, but spend most of their time idle. You are then able to run a bunch at once on 1 physical CPU that then spends much less time idle, and more time processing.

Thank you again for your detailed and easy to understand answers!

[Dave_Mishchenko]

There's a comparison of editions  here - http://www.vmware.com/products/vsphere/buy/small_business_editions_comparison.html.

If you're looking at 2 - 3 hosts the Essentials kit includes vCenter Essentials which enable management of up to 3 hosts with a single client. It makes management much easier and adds cloning, alerts, long term performance data and other management features.  The Essentials Plus kit add Data Recovery,   High Availability and vMotion.

When you create a VM the guest OS sees the actual speed of the physical CPU and is able to execute (if loaded) up to that speed.  But in reality the guest OS will often have idle time which does not require the use of CPU resources.  The ESXi CPU scheduler handles granting CPU resources to the VMs as they require it.   A virtual CPU may bounce around between physical cores depending on the load of the host.

[DSTAVERT]

You may want to have a look at some of the webstart training videos. http://communities.vmware.com/docs/DOC-14673

[Clarkington]

Thanks Guys - I'll check those videos out.

[DSTAVERT]

You might also want to check out Dave's books. I did do the ESXi training eBook offer and have started reading the book. Excellent.