Windows Various ESXi questions including running an Active Directory Domain Controller

[saspro]

Originally Posted by Chicken76

How many Vcores are there in total for how many actual physical cores? I'm trying to see how much overcommitment it's usually considered OK for production environments.

I have 12 physical & 12 hyperthreaded cores per blade & 196GB RAM per blade.

All vm's have between 2-8 vcpu's per server.

I have 95GHz total CPU resources available. I have 57GHz available

[Chicken76]

Thanks guys. That's all very useful info for me.

Originally Posted by saspro

I have 95GHz total CPU resources available. I have 57GHz available

You mean the hardware has 95 GHz total resources, and you allocated 38 to VMs leaving 57 available?

Edit: Does anyone have any experience with ESXi on AMD hardware?

[saspro]

Originally Posted by Chicken76

Thanks guys. That's all very useful info for me.


You mean the hardware has 95 GHz total resources, and you allocated 38 to VMs leaving 57 available?

Edit: Does anyone have any experience with ESXi on AMD hardware?

Correct.

There's not much difference with AMD or Intel on ESXi (unless you try moving between platforms)

[Chicken76]

Originally Posted by saspro

There's not much difference with AMD or Intel on ESXi (unless you try moving between platforms)

As I understand, moving a VM between Intel and AMD hosts is possible, but not while the VM is running. So you can't do HA, but if you shut down the VM on one host, you can start it on the other. I'm assuming the guest OS will see the new type of CPU, install drivers, etc. and probably Windows will need a reboot. Am I mistaken?

[saspro]

Originally Posted by Chicken76

As I understand, moving a VM between Intel and AMD hosts is possible, but not while the VM is running. So you can't do HA, but if you shut down the VM on one host, you can start it on the other. I'm assuming the guest OS will see the new type of CPU, install drivers, etc. and probably Windows will need a reboot. Am I mistaken?

That's what it should do.
Although you do need a good tidy up of the guest afterwards & have to re-apply IP's etc as it keeps them linked to the old missing hardware

[Chicken76]

Originally Posted by saspro

That's what it should do.
Although you do need a good tidy up of the guest afterwards & have to re-apply IP's etc as it keeps them linked to the old missing hardware

Why would the virtual NICs change when moving to a host with a different architecture?

[saspro]

Originally Posted by Chicken76

Why would the virtual NICs change when moving to a host with a different architecture?

Because it does. No logic, it's a "feature" of Windows etc

[Zoon]

For you to move a VM between hosts they need to be near enough identical, and licensed for HA - otherwise as saspro says you've gotta do it all manually.

If you're talking about a disaster recovery scenario then a couple hours may be enough for you.

Otherwise just buy two identical servers and the HA licensing required!

[Chicken76]

But if you move (manually, no HA) a VM from one Intel server to a different generation Intel server, are there any mismatches at the guest level, any detection/installation phase?

[saspro]

Originally Posted by Chicken76

But if you move (manually, no HA) a VM from one Intel server to a different generation Intel server, are there any mismatches at the guest level, any detection/installation phase?

It's a world of pain.

You can't go back generations without issues (as certain features won't exist etc), usually you find the VM won't start.

If you're moving VM's you need the same hardware.

[Chicken76]

Originally Posted by saspro

It's a world of pain.

You can't go back generations without issues (as certain features won't exist etc), usually you find the VM won't start.

If you're moving VM's you need the same hardware.

But hardware dies, goes obsolete. Is at least moving forward easier?

[saspro]

Originally Posted by Chicken76

But hardware dies, goes obsolete. Is at least moving forward easier?

Moving forwards works, it's if you only upgrade one host in your cluster you have issues.

[Chicken76]

Originally Posted by saspro

Moving forwards works, it's if you only upgrade one host in your cluster you have issues.

But even if you move forwards there's still some detection/installation involved, right?
And I suppose once that's done, moving back to the original hardware is not possible.

[saspro]

It's essentially the same as taking your old HDD and sticking it in a new machine.
Windows installs stuff and hopefully works.

You can sometimes go back but depends on what you've moved from.

[Chicken76]

But then, moving between identical machines would also mean some detection&installation, since the new hardware has other S/Ns and Windows will perceive it as different hardware.

I would have thought there was more hardware virtualization, to allow for easier migration.

[saspro]

Originally Posted by Chicken76

But then, moving between identical machines would also mean some detection&installation, since the new hardware has other S/Ns and Windows will perceive it as different hardware.

I would have thought there was more hardware virtualization, to allow for easier migration.

Migrating between identical hardware is seamless, no redetection at all.
There's no serial numbers etc in hardware to worry about.

[Zoon]

You may be able to achieve what you're looking to do with VMware Convertor.

Point it at an ESX/ESXi host and you can convert a virtual machine from one format to another.

Simply convert it to the same format and point the destination at your other host.

It'll take care of the changing hardware required in the other host.

This is not seamless and comes with its own issues. You'd only use this for a permanent transfer from one host to another.

I'd like to stress - again - that you really are best to just have an identical pair of hosts. You'd be surprised how much CPU and RAM you can get in a Dell R620 for £3000 a server and they use next to no power. With two low power quad-core CPUs and 64gb low power ram, we're looking at 137 watts for 35% load which is frankly mental.

[Chicken76]

OK, last question regarding VM transfers (for now): Is the transition easier between hosts of the same generation but different manufacturers?

[saspro]

Originally Posted by Chicken76

OK, last question regarding VM transfers (for now): Is the transition easier between hosts of the same generation but different manufacturers?

No sure I never do it.

I just buy 3 identical servers for each install

[Zoon]

If you managed to get three vendors using the exact same motherboard, CPU, network adaptors and other devices, then that would more than likely be fine.

The chances of that are small though.

You might be better considering application-level redundancy instead of working out how to migrate your guests in a hurry i.e. have two of everything. You should always have at least two domain controllers anyway but other apps often support some kind of application-level HA.