Re: [Qemu-devel] migration network requirements

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 05/20/2015 07:21 PM, Dr. David Alan Gilbert wrote:
> * Alexey Kardashevskiy (aik@ozlabs.ru) wrote:
>> Hi!
>>
>> Recent bugreports from our testers at IBM about failed migration across USA
>> (for example, from NY to TX) made me wonder - what are the actual basic
>> requirements/expectations for migration?
>
> Oh that's fun.

Was it expected to work? Our intranet is not extremely stable :)


>> In what network is it normally tested (I use 1Gb/10Gb local network without
>> routers)?
>
> That's also my main test, but in the end it's just a TCP stream, so lots of bandwidth,
> not that fussy about latency.
>
>> Is there any reconnect/restart mechanism if the connection dropped (libvirt,
>> qemu)?
>
> No; one unbroken TCP connection; if you want some reconnect/restart
> then tunnel the TCP oversomething that handles that.
>
>> Is there any document describing network requirements (libvirt, qemu)?
>
> Don't think so; libvirt has lots of different modes where it can
> tunnel stuff as well, see:
>    http://www.libvirt.org/migration.html#transporttunnel
>
>> Any ideas are appreciated :) Thanks!
>
> How is it failing?

In libvirt it looks like this (which might be unrelated):
Migration: [  0 %]error: Timed out during operation: cannot acquire state 
change lock

or this (which makes sense):
Migration: [  0 %]error: operation failed: Lost connection to destination host

The host kernel network driver can report "BUG: soft lockup" in the network 
driver. It is from quite old QEMU (2.1-ish) and host kernel though, I just 
wanted to know $subj and if it really makes sense to spend more time on this.



-- 
Alexey