A few troubleshooting questions/clarifications

[jaytee129]

Am about 6 months into using proxmox and just got a new rig (my third installation).

As I try to solve issues with Windows VMs crashing (both 10 and 11) on brand new hardware (AMD EPYC 7282 w/ Supermicro 12x mb) I'm going through different hardware configurations and am wondering if when doing h/w changes I should really consider a fresh rebuild of the VM.

For example, I started with CPU=EPYC-Rome, then changed it to "host", then to "kvm64" then back to the two others a few times as I try different things. I also add and remove a video card that is PCIe passed through. I've also tried changing the machine from q35 to i440fx. I'm thinking I might have to try other stuff, like disk controller, etc. (then rotate through all the others again with new disk controller to figure out if it's a combination of things)

So Is it safe to rotate through any/all/some of these h/w configuration options without restarting a VM build from scratch as one troubleshoots and tries to narrow down what might be the cause of the problem?

Here's more info on the problem I'm having. https://forum.proxmox.com/threads/b...md-epyc-7282-based-system.120627/#post-524007 but I'd like to know this in general (for now and later).

Any info would be appreciated.

 

[Dunuin]

At least changing between OVMF/SeaBIOS and the disk controllers/protocols (like IDE and virtio SCSI) can be problematic and Win might not be able to boot or find the old disks.

Some software can also cause problems. Keep in mind that different CPU types will allow the Guest OS to use different instructions. "Host" CPU type will allow your guest OS to use all instruction sets your physical CPU supports. But when for example using kvm64, instruction sets like AVX2 won't be available to the guestt OS, even if the physical CPU would support that. If a inatalled program then requires AVX2 instruction, it might not be able to run anymore.

 

[jaytee129]

At least changing between OVMF/SeaBIOS and the disk controllers/protocols (like IDE and virtio SCSI) can be problematic and Win might not be able to boot or find the old disks.

Some software can also cause problems. Keep in mind that different CPU types will allow the Guest OS to use different instructions. "Host" CPU type will allow your guest OS to use all instruction sets your physical CPU supports. But when for example using kvm64, instruction sets like AVX2 won't be available to the guestt OS, even if the physical CPU would support that. If a inatalled program then requires AVX2 instruction, it might not be able to run anymore.

Thanks for the reply.

Quick follow up question - is it safe to think Windows will adjust fine to a CPU change? e.g. if I do the install using kvm64 then switch to 'host' will windows now see/be able to use the additional instructions available or will it be stuck in the past (only the kvm64 instructions)?

Also, this is maybe more a windows specific question, but would a combination of hard crashes and changes to hardware break things deep inside Windows that may or may not be noticeable until later? My experience suggests more modern versions of windows recovers well from crashes but it might only look that way on the surface...