Hosts compatibility
-
As I am starting to build an environment for testing to replace VMWare, I had a question related to hardware.
When setting up multiple hosts, do these need to match the same specs (like VMWare?) for HA (moving VMs from host to host)?
I have several DELL R series servers, and some do not have the exact same CPU model or one has less memory than the other.
When setting up (HOST POOLS??) if I needed to migrate VMs, will this support different host configurations?
-
@wtdrisco said in Hosts compatibility:
As I am starting to build an environment for testing to replace VMWare, I had a question related to hardware.
When setting up multiple hosts, do these need to match the same specs (like VMWare?) for HA (moving VMs from host to host)?
I have several DELL R series servers, and some do not have the exact same CPU model or one has less memory than the other.
When setting up (HOST POOLS??) if I needed to migrate VMs, will this support different host configurations?
If the the hosts don't match by close enough, especially if their capabilities (e.g. instruction sets) and specifications. Then in the case of capabilities then the non-matching ones will be suppressed by XCP-ng so that they all match. Also when migrating the specifications, of hosts really need to match so that when VMs are placed on the hosts. There's no issues when live migrating between the each of the pool member hosts.
As the VMs expect at least a certain number of cores dependent on the hosts, and the number specified per each VM. If this number isn't met then that VM can't migrate to a specific host, which don't meet or exceed it.
-
@john-c John thanks. I get that point, but i was wondering if I had hosts that closely matching CORE counts, and similar memory, not the exact amount, but the physical CPUs would be different models and one might have 24 cores and the other 32 cores, would that prevent any movement if building it out where the VM builds did not exceed the amount the two could support (up to 24 cored defined). I hope this makes sense. I am just checking if I can mix hosts. And work within the parameters of the least. and still be able to migrate VMs (manually) or define a HA strategy across diverse hosts.
-
@wtdrisco There should be no Problem if the core counts don't match. you just can't place a VM that has 32vCPUs on the 24 core host.
But one thing you should have equal over all hosts is the amount of network interfaces and also have them configured equally (which should be done by XOA/XO form sources). Otherwise a VM might not migrate because a network Interface is missing on the target host.
Also passed through hardware might prevent migrating to another host.
I run a pool with two diffrent hosts, one has 8 Cores and one only 4 cores, also one has 64 GB RAM and the other one has only 32GB and in this limitations I can easily migrate VMs back and forth between hosts.
-
@bufanda Thank you -that was what I was hoping. I have servers that are very similar in build that will move over, but to test and start they will be different in some respects. Thank you for replying
-
@bufanda @wtdrisco What I mean by suppression of "instruction sets" is different generations of CPUs, have different extensions to the standard 64bit ones.
As the generations change you can get sometimes some of the extensions, being dropped physically from the CPU, but also new ones being added.
Since pools are supposed to all be the same, in order to cope with this the hypervisor software stack suppresses (removes or hides), the extensions to instruction sets which aren't common across other pool members.
So for instance if the majority of the pool has this https://www.intel.com/content/www/us/en/products/sku/237569/intel-xeon-gold-6544y-processor-45m-cache-3-60-ghz/specifications.html, while others of the same pool has https://www.intel.com/content/www/us/en/products/sku/139940/intel-xeon-gold-6138p-processor-27-5m-cache-2-00-ghz/specifications.html.
If you look at the instruction set extensions see which ones are, on both (these will be preserved and usable). Then which ones are not, these will be suppressed.