[Lustre-discuss] Samba and file locking

[David Noriega]

Well the samba server will be just for that, but we only have the
single filesystem '/lustre' So because of that I'm going to have to
put the flock option on all of the clients? this was my original
question.

On Mon, Aug 30, 2010 at 10:52 AM, Mark Hahn <hahn at mcmaster.ca> wrote:
>> No, we will only have a single samba server sharing out lustre-backed
>> files. What do you mean in a way similar to samba? What does samba do
>> that is different? We are using lustre to replace our old nfs server
>> for serving up home directories in our cluster and the rest of our
>> systems.
>
> what he meant is that if lustre is backing a single samba server,
> and the shared filesystem is only available via samba, you can turn
> optimize from flock to localflock.  that is, since flock is relatively
> expensive, localflock provides the behavior within a single client, such as
> the machine running samba.  if you have other lustre clients
> also mounting that filesystem, you'll need flock not localflock to provide
> consistency.
>
> -mark
>
>> On Fri, Aug 27, 2010 at 6:15 PM, Oleg Drokin <oleg.drokin at oracle.com>
>> wrote:
>>>
>>> Hello!
>>>
>>> On Aug 27, 2010, at 6:41 PM, David Noriega wrote:
>>>>
>>>> But I also found out about the flock option for lustre. Should I set
>>>> flock on all clients? or can I just use localflock option on the
>>>> fileserver?
>>>
>>> It depends.
>>> If you are 100% sure none of your other clients use flocks in a way
>>> similar to samba to
>>> guard their file accesses AND you don't export (same fs with) samba from
>>> more than one node, you
>>> can mount with localflock on samba-exporting node.
>>>
>>> Otherwise you need to mount with flock, but please be aware that flock is
>>> not exactly cheap in lustre,
>>> every flock operation is a synchronous RPC plus it puts even more load on
>>> MDS and some applications
>>> start to use flock once they see it as available resulting in possible
>>> unexpected slowdowns
>>> (MPI apps in some IO modes without lustre ADIO driver tend to do this, I
>>> think)
>>>
>>> Bye,
>>>    Oleg



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