[Lustre-discuss] need help debuggin an access permission problem

Andreas Dilger andreas.dilger at oracle.com
Fri Sep 24 08:59:42 PDT 2010

I think there is a bit of confusion here. The MDS is doing the initial authorization for the file, using l_getgroups to access the group information from LDAP (or whatever database is used).

Daniel's point was that after the client has gotten access to the file, it will cache this file locally until the lock is dropped from the client. 

Cheers, Andreas

On 2010-09-24, at 7:58, Tina Friedrich <Tina.Friedrich at diamond.ac.uk> wrote:

> Actually, what I hit was one of the LDAP server private to the MDS 
> errounously had a size limit set where the others are unlimited. They're 
> round robin'd which is why I was seeing an inermittent effect. So not a 
> client issue, the clients would not have used this server for their 
> lookups.
> Which is why I'm puzzled as to how this works, and trying to understand 
> it a bit better; to my understanding, this should not affect lookups on 
> single users, only 'bulk' transfers of data, at least as I understand this?
> Tina
> On 24/09/10 12:35, Daniel Kobras wrote:
>> Hi!
>> On Fri, Sep 24, 2010 at 09:18:15AM +0100, Tina Friedrich wrote:
>>> Cheers Andreas. I had actually found that, but there doesn't seem to be
>>> that much documentation about it. Or I didn't find it :) Plus it
>>> appeared to find the users that were problematic whenever I tried it, so
>>> I wondered if that is all there is, or if there's some other mechanism I
>>> could test for.
>> Mind that access to cached files is no longer authorized by the MDS, but by the
>> client itself. I wouldn't call it documentation, but
>> http://wiki.lustre.org/images/b/ba/Tuesday_lustre_automotive.pdf has an
>> illustration of why this is a problem when nameservices become out of sync
>> between MDS and Lustre clients (slides 23/24). Sounds like you hit a very
>> similar issue.
>> Regards,
>> Daniel.
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