Homogeneous pools, how similar do the CPUs need to be?

CodeMercenary

Oh, that's great to know @planedrop and @Andrew. While live migration would be cool, I don't know when I'd be able to set up a SAN or have a NAS big enough, fast enough and with fast enough networking, to be able to keep my VMs on it. Knowing that I can just put them in different pools and I can still offline migrate them is cool.

Are there any downsides when it comes to backups if they are in different pools? I assume XO is fine with backing up VMs in one pool to a remote in another pool.

I'm planning to put 10GB ethernet in the R630 so the servers can all communicate fast. When it comes to the XCP restrictions about ethernet ports and such, that's only if they are in pools so using separate pools eliminates that problem too, right?

The R730XD arrived while I was typing this. It's gonna be a fun weekend. Already making plans to remove the current processor and get two better ones plus add more RAM (only has two 8GB sticks right now). Nice that processors that were $2500 when this server was built are now around $100.

BobTB12

@Andrew said in Homogeneous pools, how similar do the CPUs need to be?:

@CodeMercenary ... The pool will use the features of the lowest CPU...

So this will make a pool of 5 machines with one old CPU use only the available features of the old CPU?
So if I need some newest cryptographic extensions for OpenVPN or something similar they will not be available on the whole pool if one server CPU does not support them?

Is this to support migrations only? It would be better to just say "this guest from this host can not be migrated, it has to be shut down to move" or something similar.

olivierlambert

As soon you are in a pool, it's meant to live migrate VMs around. That's why all the CPU instructions will be limited to the lowest CPU.

If you don't want to do that, just don't pool your hosts together

planedrop

@CodeMercenary To answer your questions about backups, they should all be fine, the remote is attached to XO rather than the host itself so XO can backup any VM from any host it has access to, to any remote configured in XO.

arc1

Hi,
What about joining hosts with older Intel CPUs to pool?
So if i have one pool and VMs running on hosts with newer Intel CPU (Intel Xeon Gold 6XXX) can i join two host with older Intel CPU (Intel Xeon E5-2699 v3) to that pool?
Or is better practice to create new pool with hosts with older CPUs and then migrate the VMs over?

And could migration from newer to older even can be done? Or should i shutdown the VM and then start it on host with older CPU?

olivierlambert

Yes you can
All VMs booted after the join won't use the most recent CPU features that you don't have on your old CPUs.

The only trick is for previously existing VMs with recent CPU: you need to shutdown then start then again to be sure they aren't using those features (features are applied on boot). So it's doable, but both options are possible.

Pilow

@arc1 i would suggest separate pools and use warm migration in advanced tab between pools
or shutdown VM and do a DR job or copy VM
as simple as that

arc1

Thank you both for fast answer.
Currently I prefer the option with a separate pool, as I find it more transparent.
Only one question. So currently i have ISCSI storage on cluster with newer hosts.
Can i join same storage pools to new pool with older CPU? Or do i need seperate ISCSI storage pool for new pool in XCP?

Thank you!

olivierlambert

You cannot share the same LUN between different pools (butyou can share the same SAN with different LUNs)

arc1

Thank you!
So in this case, if better option for me to join the hosts to existing pool and then shutdown VMs and start it on host with older CPUs.
Thank you again!