[pve-devel] Greatest common cluster cpuflags?
aderumier at odiso.com
Tue Sep 24 05:49:45 CEST 2013
If I remember, they are a qemu option at vm start, to test if cpuflags exists on host when starting, and stop the vm if a configured flag is missing.
If you have homegenous cluster:
-with exactly same processor : you can choose host
-with only intel or only amd, but different generation : you can choose the lowest cpu model of the generaton
-mix of amd and intel : you need to use qemu64/kvm64
Now what do you want exactly ? only a check before migration ?
----- Mail original -----
De: "Mark Casey" <markc at unifiedgroup.com>
À: pve-devel at pve.proxmox.com
Envoyé: Lundi 23 Septembre 2013 21:51:15
Objet: [pve-devel] Greatest common cluster cpuflags?
I've read that considerable performance improvements can be achieved
using a non-default kvm CPU with a VM due to the availability of
additional flags and extension sets. However I understand that this can
be troublesome for live-migration when cluster Nodes are not on
homogenous hardware. My own environment specifies a specific CPU for one
cluster that is homogenous (though I haven't benchmarked it against
defaults), but I'm stuck with defaults for another cluster which is
Intel/AMD-mixed and uses CPUs from two different generations.
Would it be possible for Proxmox to track the available cpuflags of
Nodes and store them in the shared cluster filesystem? I think this
would allow for running VMs with a greater set of cpuflags than the
default while reducing the chance of panic (or, whatever) during
live-migration. It may also be possible to compare the flags that a VM
was started with and warn if the user attempts to live-migrate it to a
Node that was added since the VM was last started (a Node which may
support fewer flags than the other Nodes, causing problems).
I have some interest in playing with this and (I think) a decent idea of
the scope of work required. Would this idea be considered simply
impossible, not likely to be adopted/merged under any circumstances, or
just currently too dangerous without extensive testing? I'm not looking
for anyone to do my homework for me or write me back a novel...but I
don't want to waste time if it for sure won't go anywhere. :D
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