[libvirt-users] live migration and config

[Dmitry Melekhov]

13.09.2018 18:57, Jiri Denemark пишет:
> On Thu, Sep 13, 2018 at 18:38:57 +0400, Dmitry Melekhov wrote:
>>
>> 13.09.2018 17:47, Jiri Denemark пишет:
>>> On Thu, Sep 13, 2018 at 10:35:09 +0400, Dmitry Melekhov wrote:
>>>> After some mistakes yesterday we ( me and my colleague ) think that it
>>>> will be wise for libvirt to check config file existence on remote side
>>> Which config file?
>>>
>> VM config file, namely qemu.
> Do you mean the domain XML definition found in /etc/libvirt/qemu/*.xml ?
Yes and no, xml, but at another location.

>
>> We forgot to mount shared storage (namely gluster volume), on which we
>> have config files, twice...
> If you're talking about the domain XML file, then you should never store
> them on a shared storage. All XML files in /etc/libvirt are supposed to
> be local to each host.

They are not stored in /etc/libvirt , but in other location, which is 
suitable for sharing.


>   Sharing them may cause changes done on one host
> will not be seen by libvirtd on the other host and they can even get
> lost when libvirtd on the other host decides to write its version of the
> domain definition to the file.
>
> And migration is designed so that the domain definition does not need to
> be present on the destination host. In fact, even if it's present,
> libvirtd will ignore it until you stop the migrated domain and start it
> again.

Sounds strange, because if there is no config file on target host 
migration fails, always.
>
>> And tried to live migrate VM to another host, where there is no config
>> file, so VM can't be started, so it died. Twice :-(
> Error messages or logs would help. Otherwise we have no clue what failed
> and why.
>
>
Unfortunately, my colleague left today  for 2 weeks vacations and I have 
no access to these hosts,
so I will be able to look in logs or do some tests only in October.
So, I'll write there again after 2 weeks or so.

Thank you!