[Lustre-discuss] Samba and file locking

[Oleg Drokin]

Hello!

Similar as in some app whose locking would conflict with samba locks in a way to protect
updates by samba from updates from those apps at the same time should they happen
in the same moment of time.
Now that I think about it, I remember that samba does not really use flock, but
rather some oplocks which have different posix lock op codes that lustre
does not implement, so mounting with localflock is the only way to get that
functionality, but it is important to remember that it won't be cluster-coherent
(so would only be visible locally to that samba-exporting node).
Typically cluster-coherence would only be important when you have more than one
samba-exporting node, though.

Bye,
    Oleg

On Aug 30, 2010, at 11:47 AM, David Noriega 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.
> 
> 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
> 
> 
> 
> -- 
> Personally, I liked the university. They gave us money and facilities,
> we didn't have to produce anything! You've never been out of college!
> You don't know what it's like out there! I've worked in the private
> sector. They expect results. -Ray Ghostbusters
> _______________________________________________
> Lustre-discuss mailing list
> Lustre-discuss at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-discuss