Re: [linux-lvm] LVM snapshot with Clustered VG [SOLVED]

[Zdenek Kabelac <zkabelac@redhat.com>]

Dne 15.3.2013 10:29, Vladislav Bogdanov napsal(a):
> 15.03.2013 12:00, Zdenek Kabelac wrote:
>> Dne 14.3.2013 22:57, Andreas Pflug napsal(a):
>>> On 03/13/13 19:30, Vladislav Bogdanov wrote:
>>>>
>>>>> Is there a way to find out if a LV is locked exclusively? lvs
>>>>> displaying
>>>>> -e-- instead of -a-- would be nice. Seems not even lvdisplay knows
>>>>> about
>>>>> exclusive locking.
>>>> That would break other tools which rely on their output. F.e. cluster
>>>> resource agents of libvirt (yes, it runs lvm tools rather then using
>>>> API, which is not yet complete btw). As I also need to obtain this
>>>> information, I think about writing simple tool (f.e. clvm_tool) which
>>>> would display needed info.
>>>>
>>>> As a workaround you can run lvchange -aly without force parameter. If it
>>>> succeeds, the volume is locked in a shared mode, otherwise it is locked
>>>> exclusively.
>>>
>>> Hm, thats one ugly workaround...
>>> How about a clvmd option, something like -l to list all locks and exit.
>>>
>>
>>
>> I think - the extension to  'lvs' command could be relatively simple
>> (adding a new column)
>
> Yes, that's correct.
>
>>
>> You may query  for  exclusive/local activation on the node.
>> (So you cannot just tell on which other node is the device active,
>> but you could print about these states:
>>
>> active exclusive local
>> active exclusive
>> active local
>> active
>
> You also may poll all know nodes, but that is a hack too.
>
> That's why I prefer to have this as a separate tool (with dlm_tool-like
> params and output) which lists node IDs and lock mode. Unfortunately do
> not have power to write it now.
>
> Are core LVM devels interested in these two features: lock conversion
> and managing remote node locks? If yes, then I can (hopefully) prepare
> git patches next week.


I'm not quite sure what do you mean by  'managing remote node locks' ?

Current login behind lvm command is  -

You could activate LVs with the above syntax [ael]
(there is a tag support - so you could exclusively activate LV on remote
node in via some configuration tags)

And you want to 'upgrade' remote locks to something else ?

What would be the use-case you could not resolve with current command line args?

Is that supported by dlm (since lvm locks are mapped to dlm)?
How would you resolve error path fallbacks ?
Also I believe the clvmd protocol is out of free bits for extension,
so how the protocol would look like ?

Zdenek