I'm attempting to establish an absolute maximum, byte-rate performance
value, running a bare bones MPI_File_write_all_at benchmark program, for
our Cray XT3 installation, RedStorm, here at Sandia National
Laboratories. Processor time is at a premium, and I only run in the
standard queue, so I'm not able to do everything I would imagine, though
maybe what I can run is adequate.
I have a directory under our Lustre, redstorm:/scratch_grande which I
have defined with:
lfs setstripe -1 0 -1
Though there are 320 OST's comprising the FS, these defaults give me a
stripe_count of 160 (I'm sure someone could explain that), and I don't
know the stripe_size. With a job of 160 processors, each of which has a
contiguous chuck of 20 MB of memory, respectively, to append to an open
file in an iterative series of singular, atomic, write_all operations, I
can normally average 25 GB/s. To curb any confusion here, that
represents only an experimental maximum to me; none of our many,
complex, science and engineering simulation applications perform their
output dumping with per-processor blocks as large as a single MB.
I would like any succinct suggestions on explicitly setting my lfs
stripe_size, given the configuration and parameters I've mentioned here,
to optimize it and, perhaps see a decrease in the time spent storing my
data on the FS.
Thank you,
Marty Barnaby
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