[one-users] opennebula 3.8.1 + clvm

[Jaime Melis]

Hi Marlok,

I agree with what you said, it would be much better to remove the
requirement of CLVM, but I have a couple of concerns.  Let's see if we can
find a solution to that together and decide if we can squeeze this one in
for OpenNebula 4.0. Let me explain you the main problem I see.

So, the main concern here is that in the shared_lvm TM drivers, you're
operating directly on the frontend, and I think that will pose a problem if
you want to have multiple LVM based datastores. I don't think it's a
correct approach to force the OpenNebula admins to use the OpenNebula
frontend as their LVM primary node.

If you take a look at the DS/LVM drivers in the 'master' branch, you'll see
that we extract the LVM primary node's hostname via the 'HOST' attribute of
the datastore template [1]
The problem is, that we don't have that information in the TM drivers. A
solution would be to execute "onedatastore <id>" and extract the
datatostore's LVM primary node for each operation: cp, ln, mvds, etc...

One we have we have the name of the lvm primary node, we could follow your
approach: operate (clone, create, remove, etc...) in that node and refresh
it the nodes via lvscan and lvchange...

any thoughts?

[1]
https://github.com/OpenNebula/one/blob/master/src/datastore_mad/remotes/lvm/clone#L56

cheers,
Jaime


On Tue, Mar 12, 2013 at 11:41 AM, Marlok Tamás <tmarlok at sztaki.hu> wrote:

> Hi Jaime,
>
> I examined the new lvm driver and compared it with shared_lvm.
> I think, the only difference between them, is that in shared_lvm all of
> the lvm commands are executed on the frontend (as we described in here:
> http://wiki.opennebula.org/shared_lvm).
> I would like to suggest, that you should consider to adapt this behaviour
> in the new lvm driver.
> (Or in the case of the one driver, the HOST configured in the datastore
> config should execute this commands, but not the host, running the VM.)
>
> I can't see any drawback of this approach, but in this way, CLVM wouldn't
> be necessary (refer the wiki article).
>
> We couldn't use CLVM for various reasons, but it would be much easier for
> us (I think not just for us) if we could use the LVM driver already
> implemented in OpenNebula, instead of shared_lvm.
>
> I see, that in the datastore driver scripts this is the current behaviour.
> So only the tm scripts should be modified.
>
> If you can agree with this, but don't have the time for implementing, just
> let me know, I can create a patch for you. Or if I am wrong let me know
> that too :).
>
> Cheers,
> Tamas
>
>
> On Thu, Feb 21, 2013 at 6:52 PM, Jaime Melis <jmelis at opennebula.org>wrote:
>
>> Oops, you're right.
>>
>> Ok, so, can you test the upcoming LVM drivers for OpenNebula 4.0? It
>> replaces snapshotting with cloning...
>>
>> just replace /var/lib/one/remotes/tm/lvm
>> with the contents of:
>> https://github.com/OpenNebula/one/tree/master/src/tm_mad/lvm
>>
>> and do "onehost sync" afterwards?
>>
>>
>> On Thu, Feb 21, 2013 at 6:41 PM, Tobias Honacker
>> <t.honacker at googlemail.com>wrote:
>>
>> > Hi Jaime,
>> >
>> > yes you are right. I posted the error log file with TM_MAD="lvm", too. I
>> > tried both TM_MAD=shared and lvm.
>> > I will try the links Mihály Héder already posted. But maybe you have got
>> > any other ideas?
>> >
>> >
>> > Best regards,
>> > Tobias
>> >
>> >
>> > Am 21.02.2013 um 18:37 schrieb Jaime Melis:
>> >
>> > Actually, it's "onedatastore update 100", not "onetemplate"... sorry
>> >
>> >
>> > On Thu, Feb 21, 2013 at 6:22 PM, Jaime Melis <jmelis at opennebula.org
>> >wrote:
>> >
>> >> Hi Tobias,
>> >>
>> >> your datastore template has the wrong TM_MAD. It should be TM_MAD="lvm"
>> >> instead of TM_MAD="shared".
>> >>
>> >> You can fix it by doing "onetemplate update 100" and editing it
>> in-place
>>
>
>


-- 
Jaime Melis
Project Engineer
OpenNebula - The Open Source Toolkit for Cloud Computing
www.OpenNebula.org | jmelis at opennebula.org
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