Andreas Dilger wrote: > 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. >
Andreas, Has anyone reported results of an SSD based MDT? Craig >> 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 > -- Craig Tierney ([email protected]) _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
