Default Host Type

[dpearceFL]

As we discovered with the Storage Review of Hypervisors, the default host type incurs a performance penalty. I would like to suggest a better "default" setting.

With a single node, any setting other than "host" is pointless.

In a cluster of multiple nodes all with the same CPU type, any settings other than "node" is pointless.

In a cluster of multiple nodes with different types of CPUs, can't Proxmox figure out what the lowest common denominator is?

In the latter case, this CPU type setting is important is you want to live migrate a VM from one host to another. If you want to do a migration of a stopped VM, leave the type set to "host".

If this is too much "figuring out" for he Proxmox Devs, may I suggest the default be changed to "host".

 

[dpearceFL]

Storage Review has updated their post, adding "Optimized Proxmox":

In our new tests, optimized Proxmox uses host as CPU type, NUMA Enabled, q35 as Machine, and OVMF (UEFI) as BIOS. Cache was set to Write Back for storage since we are using a Raid Controller, and SSD Emulation was turned on.

https://www.storagereview.com/revie...rformance-of-leading-virtualization-solutions

 

[LnxBil]

AFAIK, the review still has not squeezed the same power out of PVE as ESXi does. I read that ESXi disables all spectre mitigations and PVE does not. Therefore the performance of PVE is still worse, yet it is more secure. The same is true for the restricted instruction set CPUs that are used in KVM. It would not be the default if there would be something better.

 

[dpearceFL]

The same is true for the restricted instruction set CPUs that are used in KVM. It would not be the default if there would be something better.

I respectfully disagree. The "default" host type removes many of the optimizations modern CPUs have. Just look at that article's results comparing Proxmox (default) vs Proxmox Opi (host). Huge increases when using the host settings.

 

[dpearceFL]

The default setting of the host type is a matter of great discussion. See https://bugzilla.proxmox.com/show_bug.cgi?id=1564

Using the default CPU type will dumb down the emulated CPU. In Proxmox VE 8.2.4 the default is "x86-64-v2-AES". This is equivalent to Westmere or Opteron_G4 CPUs.

The default is the default because is the most compatible with the most CPUs. Host will always be the most performant.

 

[dpearceFL]

Host will always be the most performant.

Depending on the type of CPU load. Very simple tests like prime number generation show no difference.

 

[LnxBil]

Host will always be the most performant.

depending on the workload as you already stated and...

Very simple tests like prime number generation show no difference.

The same is true for 99% of all software unless specifically optimized. Most software does not can cannot use the features.

There are no instruction set extensions that will benefit raw io power, so no magic switch and everything is fine. AVX and AES are the most important extensions I know of. Having the default to kvm will ensure working live migration, type=host will not.

If this is too much "figuring out" for he Proxmox Devs, may I suggest the default be changed to "host".

This will break live migration and is the worst default you can have. Just spin up a nested hypervisor with host and try to migrate or search the forum for type=host and live migration. you will end up with a lot of entries complaining about problems.