On Oct 23, 2008 16:06 +0200, S�bastien Buisson wrote: > We are using MPI-IO on Lustre, so that we can achieve good performance > when writing or reading the same file from multiple processes and clients. > In the shared pointers read/write routines, MPI-IO makes an intensive > use of file locks (for instance, see the file > src/mpi/romio/adio/common/ad_get_sh_fp.c from mpich2-1.0.7). The problem > is that file locking support in Lustre is very limited today: > - there is the localflock option for the local mode. In this mode, locks > are coherent on a node (a single-node flock), but not across all clients; > - there is the flock option for the consistent mode. In this mode, locks > are coherent across all clients. But the Lustre Operations Manual > includes a big warning about this mode, saying that it can affect > performance and stability. > > That being said, does anybody in the Lustre community know about current > alternatives to the MPI-IO shared pointers read/write routines, which do > not use the file locking mechanism but provide the same functionality?
Tom Wang is our MPI-IO expert, and has done a lot of work to improve the performance of MPI-IO with Lustre, so he can probably answer this question better than I can. > By the way, do we have an idea of the Lustre version that will provide > the reliable version of the flock consistent mode? There are in fact a number of users that enable the flock support in conjunction with MPI-IO already. The reason we haven't made it enabled for general usage is that there may still be some bad interactions with flock under less well-behaved applications. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
