Which versions are you using in servers and clients? On Wed, May 20, 2015 at 12:40 AM, Schneider, David A. < david...@slac.stanford.edu> wrote:
> I am trying to get good performance with parallel writing to one file > through MPI. Our cluster has high performance when I write to separate > files, but when I use one file - I see very little performance increase. > > As I understand, our cluster defaults to use one OST per file. There are > many OST's though, which is how we get good performance when writing to > multiple files. I have been using the command > > lfs setstripe > > to change the stripe count and block size. I can see that this works, when > I do lfs getstripe, I see the output file is striped, but I'm getting very > little I/O performance when I create the striped file. > > When working from hdf5 and mpi, I have seen a number of references about > tuning parameters, I haven't dug into this yet. I first want to make sure > lustre has the high output performance at a basic level. I tried to write a > C program uses simple POSIX calls (open and looping over writes) but I > don't see much increase in performance (I've tried 8 and 19 OST's, 1MB and > 4MB chunks, I write a 6GB file). > > Does anyone know if this should work? What is the simplest C program I > could write to see an increase in output performance after I stripe? Do I > need separate processes/threads with separate file handles? I am on linux > red hat 5. I'm not sure what version of lustre this is. I have skimmed > through a 450 page pdf of lustre documentation, I saw references to > destructive testing one does in the beginning, but I'm not sure what I can > do now. I think this is the first work we've done to get high performance > when writing a single file, so I'm worried there is something buried in the > lustre configuration that needs to be changed. I can run /usr/sbin/lcntl, > maybe there are certain parameters I should check? > > best, > > David Schneider > _______________________________________________ > lustre-discuss mailing list > lustre-discuss@lists.lustre.org > http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org > -- Nguyen Viet Cuong
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