[ovirt-users] migration of a VM: fails

[Francesco Romani]

On 05/23/2017 04:29 PM, cmc wrote:
> Hi Francesco,
>
>> do you always have the same error?
> Yes

Interesting, but this doesn't tell us much

>
>> Are you by any chance using the post copy migration mode?
> Not sure what that is. The migration is initiated by either putting
> the host in maintenance, or selecting 'upgrade' from the menu.

Postcopy migration is a new live migration mode that performs
differently from the old one (called precopy migration).
In some scenarios does wonders, in some others... no :)
If you don't know about it, it's likely you are using the defaults, so I
can check myself (also from the libvirt logs).

Please note that from Vdsm perspective there is no difference between
user-initiated migration, migrations
started because the host goes in maintenance, or any other trigger of
migration: they all kickstart the same flow.

>
>> Could you please share the libvirt debug logs, at least on the source side?
>>
>> https://wiki.libvirt.org/page/DebugLogs
>>
>> You may want to do a test run with the debug logs turned on and disable them
>> just after, those are VERY verbose.
>>
> Before I put it into debug mode, I'd tried to migrate the troublesome
> VM by itself, and it worked. So I then thought I try putting the host
> that has that VM into maintenance, and it successfully copied that VM
> over, but failed on another VM this time (a Linux VM). I took the host
> out of maintenance, and switched on debug mode (restarting libvirtd
> made the host rather unhappy, but it sorted itself out), and then
> tried putting the host back into maintenance. It complained about
> another VM failing to be migrated, though I couldn't see that VM on
> the host. It did succeed in moving the VM that was causing it
> problems, and is now in maintenance mode. So it seems a bit hit and
> miss. Do you still want the logs?

Thanks for your investigations. The issues you are facing definitely
point in the direction of low layers of the stack.
We may learn something helpful from the libvirt logs, since you already
have it could be worth looking at them.

So if you want to share them, I'll have a look.

-- 
Francesco Romani
Senior SW Eng., Virtualization R&D
Red Hat
IRC: fromani github: @fromanirh