Hi Stefan,
Thanks for your reply!
MJ
On 2/26/20 4:14 PM, Stefan Reiter wrote:
Hi!
On 2/26/20 3:35 PM, mj wrote:
Hi,
Just to make sure I understand something. We have an identical
three-node hyperconverged pve cluster, on Intel Xeon CPU's.
Now we would like to expand, and we are investigating what path to
choose.
The way we understand it is: if we would like to do live migrations
between pve hosts, the servers need to have similar CPUs, or otherwise
we need to virtualise the CPU as well. (so set CPU type to kvm64)
Note that even kvm64 does not really work for cross-vendor
live-migrations (i.e. AMD <-> Intel as mentioned in subject). This was
recently discussed on the pve-devel list [0], as well as an older bug
report [1].
[0] https://pve.proxmox.com/pipermail/pve-devel/2020-February/041750.html
[1] https://bugzilla.proxmox.com/show_bug.cgi?id=1660
In case it matters: 90% of our VMs are debian 9/10 hosts.
While we could do change to kvm64, we currently use cpu type 'host',
and we wonder how much performance kvm64 would cost us, and what
potential other drawbacks this could have.
Aside from the above, the performance impact of switching to kvm64 is
largely dependent on the software you are running within your VM. Raw
CPU performance will stay the same, but most hardware acceleration (e.g.
AES for encryption or AVX) will not be available to the guest.
If the CPUs are from the same vendor, you can most likely enable the
older generation CPU type for your VMs and still get away with
live-migration. This way you can use _most_ acceleration features, and
are just missing out on any new ones introduced in the newer CPU gen.
Has anyone ever done much testing on this subject? Anyone with
interesting insights / knowledge / experiences to share on this subject?
MJ
Hope that helps,
Stefan
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