Interesting discussion of NFS vs. Lustre even if they are so different in aims...
[ ... ] lee> 3) It must support all of the transports we are interested in. Except for some corner cases (that an HEP site might well have) that today tends to reduce to the classic Ethernet/IP pair... lee> 4) It must be scalable, in that we can cheaply attach lee> storage and both performance (reading *and* writing) and lee> capacity within a single mounted file system increase in lee> direct proportion. I suspect that scalability is more of a dream, as to me it involves more requirements including scalable backup (not so easy) and scalable 'fsck' (not so easy). These are easier with Lustre because it does not provide "a single mounted file system" but a single mounted *namespace* which is a very different thing, even if largely equivalent for most users. [ ... ] lee> NFS4 does most everything Lustre can with one very lee> important exception, IO bandwidth. [ ... ] Lustre IO lee> performance *does* scale. It uses a 3rd-party transfer. That can summarized by saying that Lustre is a parallel distributed metafilesystem, while NFS is a protocol used to access what usually is something not distributed and an actual filesystem. The limitations of the NFS protocol can be overcome, and as you say, pNFS turns it into a parallel distributed metafilesystem too: lee> NFS4 has a proposed extension, called pNFS, to address this lee> problem. It just introduces the 3rd-party data transfers lee> that Lustre enjoys. If and when that is a standard, and is lee> well supported by clients and vendors, the really big lee> technical difference will virtually disappear. It's been a lee> long time coming, though. It's still not there. Will it lee> ever be, really? My impression is that it is a lot more real than it was only a couple years ago, and here is an amusing mashup: http://FT.ORNL.gov/pubs-archive/ipdps2009-wyu-final.pdf «Parallel NFS (pNFS) is an emergent open standard for parallelizing data transfer over a variety of I/O protocols. Prototypes of pNFS are actively being developed by industry and academia to examine its viability and possible enhancements. In this paper, we present the design, implementation, and evaluation of lpNFS, a Lustre-based parallel NFS. [ ... ] Our initial performance evaluation shows that the performance of lpNFS is comparable to that of original Lustre.» lee> Done. That was useful for me. I think five years ago I lee> might have opted for Lustre in the "create many small lee> files" case, where I would consider NFS today, Looks optimistic to me -- I don't see any good solution to the "create many small files case, at least as to shared storage. For smaller situations I am looking out of interest to some other distributed filesystems, which are a bit more researchy, but seem fairly reliable already. _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
