On 2012-02-15, at 3:58 AM, Jack David wrote: > On Wed, Feb 15, 2012 at 5:00 PM, Peter Grandi <[email protected]> > wrote: >>> Once the lustre client knows about the stripe information of a >>> file, will it directly communicate to OSS? >>> >>> If yes, is there any optimization possible if lustre client >>> learns that the data is in the same machine (when acting as >>> OST) ? >> >> Not directly. RPCs may be rather faster locally than over a >> network interface. > > Hmm, but it will still involve multiple memory copy operations to > transfer data from _local_ client to _local_ OST, correct? Can that be > avoided? or The client is smart enough to share the memory when it > knows the client and OST are the same machine.
There is still a memory copy, but it is internal to the LNET code for the lo@0 interface and is not being passed over e.g. the TCP loopback or ethernet lo interface. It would be desirable to have a more efficient OSC->OSD interface for local IO, but as yet there hasn't been any work in this direction. Cheers, Andreas -- Andreas Dilger Whamcloud, Inc. Principal Lustre Engineer http://www.whamcloud.com/ _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
