[pve-devel] adding live migration options ? (xbzlre, compression, ...)

Alexandre DERUMIER aderumier at odiso.com
Fri Sep 25 13:44:08 CEST 2015


I have tested xbzrle & compression.

xbzrle seem to be pretty fine, I don't have bug with it. (tested with video player running in guest)
also they are no overhead on 10gbe network

without xbzlre:
Sep 25 12:52:18 migration speed: 1092.27 MB/s - downtime 66 ms

with xbzlre:
Sep 25 13:30:17 migration speed: 1129.93 MB/s - downtime 162 ms



now for compression (default option), I have a big big overhead

Sep 25 13:36:39 migration speed: 352.34 MB/s - downtime 450 ms
and source kvm process jump to 800% (on a xeon-e5 3,1ghz)


I think we can enable xbzrle by default, but for compression,
I really not sure it's a good idea. (depend on cpu/network bandwith)



----- Mail original -----
De: "dietmar" <dietmar at proxmox.com>
À: "aderumier" <aderumier at odiso.com>
Cc: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Jeudi 24 Septembre 2015 11:45:08
Objet: Re: [pve-devel] adding live migration options ? (xbzlre, compression, ...)

> >>I think those are special cases, and it is always better to enable 
> >>compression, 
> >>because 
> >>it reduces traffic on the network. 
> 
> the kvm forum slides, they said that with compression, the migration is slower 
> 
> on 10gbit network. 

Don't get me wrong, but this depends on many, many factors. I am sure this is 
true 
if you run a single migration. But the picture is totally different if you run 
on a real network which is used by many other VMs. Or if you run more than one 
migration 
at same time. 

> >>But do we already use lz4? 
> Currently we don't have implemented live migration compress. (it's a new 
> feature from qemu 2.4) 
> 
> 
> I'll make a basic patch to enable compression, and will do some benchmark with 
> 10gbe network. 

Great. 


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