On Wed, Feb 15, 2012 at 5:00 PM, Peter Grandi <[email protected]> wrote: >> I have a small lustre setup having 1 MDS, 2 OSS and all of the >> three machine also have lustre client mounted. > > Note that running the Lustre client on a Lustre server is not > recommnended because there can be a resource deadlock between > the client and server modules (involving the cache IIRC). > > However I suspect that this problem occurs only on OSSes, and I > suspect that it is negligible on the MDS. > > Which makes me suspect that running some types of workloads on > the MDS as a client may give some advantages. > >> Once the lustre client knows about the stripe information of a >> file, will it directly communicate to OSS? > > After fetching the file metadata from (one of) the MDS(es) > Lustre clients always communicate directly with the OSS(es) > involved. That's the whole point of having distinct metadata > and data servers. > Right, I agree.
> A coarse way of understanding Lustre and similar filesystem > types is to imagine that Lustre clients can "mount" invidual > files (or strips of a file) from an OSS, and the MDS is the > server with the automount maps. > >> 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. Thanks J _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
