On 2009-12-02, at 09:20, Francois Chassaing wrote: > I have a big fundamental question : > if the load that I'll put on the FS is more IOPS-intensive than > throughput-intensive (because I'll access lots of medium-sized files > ~5 MB from a small number of clients), should I better go Lustre or > PVFS2 ?
I don't think PVFS2 is necessarily better at IOPS than Lustre. This is mostly dependent upon the storage configuration. > Also, if the main load is IOPS, shouldn't I oversize MDS/MDT in > terms of CPU/RAM and storage perf (ie. : max of 15K SAS RAID10 > spindles possible) ? The Lustre MDS/MDT is used only at file lookup/open/close, but is not involved during actual IO operations. Still, this means in your case that the MDS is getting 2 RPCs (open + close, which can be done asynchronously in memory) for every 5 OST RPCs (5MB read/write, which happen synchronously), so the MDS will definitely need to scale but not necessarily at 2/5 of the total OST size. Typical numbers for a high-end MDT node (16-core, 64GB of RAM, DDR IB) is about 8-10k creates/sec, up to 20k lookups/sec from many clients. Depending on the number of files you are planning to have in the filesystem, I would suggest SSDs for the MDT filesystem, especially if you have a large working set and are doing read-mostly access. > on the budget side, may I use asynchronous DRBD to mirror MDT > (internal storage), or should I only got a good shared storage > (direct or iscsi) ? Some people on this list have used DRBD, but we haven't tested it ourselves. I _suspect_ (though have not necessarily tested this) that if you are using DRBD it would be possible to have lower-performance storage on the backup server without significantly impacting the primary server performance, if you are willing to run slower in the rare case when you are failed-over to the backup. > Today I'm leaning towards Lustre, because I've tested it against > glusterfs, and gluster performed little less good than lustre but > poorly failed the bonnie++ create/delete tests. Also I didn't gave a > shot at PVFS2 yet... 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
