[ovirt-users] thin_check run on VM disk by host on startup ?!

[Rik Theys]

On 08/31/2016 09:43 AM, Rik Theys wrote:
> On 08/30/2016 04:47 PM, Nir Soffer wrote:
>> On Tue, Aug 30, 2016 at 3:51 PM, Rik Theys <Rik.Theys at esat.kuleuven.be> wrote:
>>> While rebooting one of the hosts in an oVirt cluster, I noticed that
>>> thin_check is run on the thin pool devices of one of the VM's on which
>>> the disk is assigned to.
>>>
>>> That seems strange to me. I would expect the host to stay clear of any
>>> VM disks.
>>
>> We expect the same thing, but unfortunately systemd and lvm try to
>> auto activate stuff. This may be good idea for desktop system, but
>> probably bad idea for a server and in particular a hypervisor.
>>
>> We don't have a solution yet, but you can try these:
>>
>> 1. disable lvmetad service
>>
>>     systemctl stop lvm2-lvmetad.service lvm2-lvmetad.socket
>>     systemctl mask lvm2-lvmetad.service lvm2-lvmetad.socket
>>
>> Edit /etc/lvm/lvm.conf:
>>
>>     use_lvmetad = 0
>>
>> 2. disable lvm auto activation
>>
>> Edit /etc/lvm/lvm.conf:
>>
>>     auto_activation_volume_list = []
>>
>> 3. both 1 and 2
>>
> 
> I've now applied both of the above and regenerated the initramfs and
> rebooted and the host no longer lists the LV's of the VM. Since I
> rebooted the host before without this issue, I'm not sure a single
> reboot is enough to conclude it has fully fixed the issue.
> 
> You mention that there's no solution yet. Does that mean the above
> settings are not 100% certain to avoid this behaviour?
> 
> I was thinking of setting a global_filter in /etc/lvm/lvm.conf to only
> include the PV's for the hypervisor disks (on which the OS is installed)
> so the system lvm commands only touches those. Since vdsm is using its
> own lvm.conf this should be OK for vdsm?

This does not seem to work. The host can not be activated as it can't
find his volume group(s). To be able to use the global_filter in
/etc/lvm/lvm.conf, I believe it should be overridden in vdsm's lvm.conf
to revert back to the default.

I've moved my filter from global_filter to filter and that seems to
work. When lvmetad is disabled I believe this should have the same
effect as global_filter? The comments in /etc/lvm/lvm.conf indicate also
udev might ignore the filter setting?

Rik

-- 
Rik Theys
System Engineer
KU Leuven - Dept. Elektrotechniek (ESAT)
Kasteelpark Arenberg 10 bus 2440  - B-3001 Leuven-Heverlee
+32(0)16/32.11.07
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