On Nov 11, 2006 15:04 -0800, Lin Shen (lshen) wrote: > In talking to the application team, they think there are a > number of reasons that NFS is not good enough. Do you think Lustre can > adequately address the following issues? > > 1) NFS adds too many data copies and complex marshaling of messages. > Particularly for virtual memory paging, this is a performance killer.
Lustre supports O_DIRECT and RDMA network transfers (zero-copy send only for TCP). With O_DIRECT IO and, say, Infiniband, it is possible to have no data copies (except RDMA over the network) all the way to the disk. > 2) NFS directory traversal is very slow because every path element > requires message exchanges between client and server. This means that > administrative tasks like backups are really expensive. Lustre is the same in this regard currently. > 3) NFS locking has always been problematic, sometimes with deadlock > cases, sometimes problems with recovery after node failure. Simultaneous > access of a single file from multiple nodes has additional caching and > other coherency problems. Lustre has full data coherency between clients. > 4) NFS doesn't provide any notion of raw device access so the > optimizations created in storage layers running on top of NFS > (databases, specialized file systems, etc.) don't work as expected. This is O_DIRECT, or something else? > 5) The layering of volume management under NFS doesn't really work. If > the storage media is spread across several nodes, with the NFS server > located on a single node, the read/write requests have to move from > client to server to media node. With a cluster file system, the > read/write requests should always be from client to media node. This is the case with Lustre - that client IO is always directly (and only) to the storage node(s) that contains the data. A single file can be striped over multiple storage nodes. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. _______________________________________________ Lustre-discuss mailing list [email protected] https://mail.clusterfs.com/mailman/listinfo/lustre-discuss
