[Lustre-discuss] Lustre and VFS calls

[Andreas Dilger]

On Jun 24, 2008  17:35 -0700, Huang, Eric wrote:
> Got another question, does Lustre provide a different user level library
> to access the file system? I mean, when the user application does a
> "read" or "write", is it using the regular Linux library to conduct
> these system calls? Or does Lustre provide its own, such that these
> "read" and "write" calls are not typical VFS calls anymore? My
> understanding is that Lustre has its own user-level library that
> intercepts these system calls and send commands across Lnet to get/write
> data. Only the meta-data related calls (such as INODE allocation,
> deletion, etc.) are actually passed to VFS. Am I right?

No, Lustre is a regular filesystem that is POSIX compliant.  There
IS a userspace Library for Lustre, but that is used only for a
very limited class of systems, normally the Catamount clients on
the Cray XT3, and if non-Linux clients are using FUSE to access
Lustre (e.g. OSX, FreeBSD).

> -----Original Message-----
> From: Andreas.Dilger at sun.com [mailto:Andreas.Dilger at sun.com] On Behalf
> Of Andreas Dilger
> Sent: Monday, June 23, 2008 3:56 PM
> To: Huang, Eric
> Cc: Nikita.Danilov at sun.com
> Subject: Re: [Lustre-discuss] Lustre and memory-mapped I/O
> 
> On Jun 19, 2008  10:18 -0700, Huang, Eric wrote:
> > Here is the error:
> > 
> > *** USER FATAL MESSAGE 1250 (BIOCRT)
> >      STATUS =           38, FILX =    3, LOGNAME = MASTER  , NSBUF3 =
> > 65536
> >      FILE = /lustre/client/4way/xx0cmd0.T18856_24.t7.MASTER
> >      ERROR MESSAGE IS --
> >      Function not implemented (errno = 38)
> >  *** SYSTEM FATAL MESSAGE 446 (DBCRT)
> >      ERROR ATTEMPTING TO CREATE A FILE (LOGICAL= MASTER  ) FOR DBSET
> > MASTER WITH READ AND WRITE PRIVILEGES.
> >      USER ACTION: CHECK THE AVAILABLE/ALLOCATED SPACE AND THE
> PRIVILEGES
> > GRANTED THIS ACCOUNT.
> >  
> >     USER INFORMATION: THIS ERROR OCCURS WHEN MORE THAN ONE JOB HAS
> WRITE
> > PRIVILEGE AT THE SAME TIME.
> >                ONLY ONE JOB CAN HAVE WRITE PRIVILEGE.
> > 0FATAL ERROR
> > 1                                        * * * END OF JOB * * *
> > 
> > 
> > I think it may have to do with the Lustre lock implementation. The
> > directory /lustre/client/4way is a directory with file-striping set to
> 4.
> 
> Is this application trying to use flock?  Then the client needs to
> be mounted with flock support, either "-o flock" to enable distributed
> flock (lower performance), or "-o localflock" (for local node flock
> only,
> if application only needs flock on a single node).
> 
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.