Hi,
I noticed that xl now uses an ssh-tunnel to do live-migrations.
At the first look I thought: Nice idea. This makes live-migrations secure without reinventing the wheel. This also drops the need to implement an own transfer protocol.
Well – so I tried my first live-migration with my shiny new servers with thick 10GB-network lines…
There is a severe bottleneck here: Since both the standard ssh-server and ssh-client are not able to use more than one CPU, the rate of a single CPU will limit the
transfer speed.
So what are possible solutions?
First thought:
Contact the XEN-developers and ask for multiple ssh-sessions for the live-migration. This is propably hard to code since you would need to partition memory of the DomU
and start/control a number of transfer threads.
Second thought:
Why is ssh not multi-threaded?
Well after searching a bit I found such a project:
http://www.psc.edu/index.php/hpn-ssh
Two drawbacks:
·
You loose encryption completely, or are restricted to just one cipher
·
You need to patch openssh and rebuild it
What other alternatives exist to make use of the full available bandwidth for live-migrations on the xl-stack?
Especially when using secure networks for live-migration (ie. private network, only seen on the Dom0s)?
Kind regards
Nils
