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Re: [bgl-discuss] Blue Gene slow I/O
Could you give us a few more details? Is each process writing to a
separate file, with all processes writing at about the same time?
Are they writing contiguous blocks to the same file, with the blocks
aligned on block boundaries? Are they writing multiple segments to
the same file, with each process contributing some set of segments?
Do you use MPI-IO? If so, which MPI-IO routines do you use? If not,
would you be willing to consider using MPI-IO?
Thanks!
Bill
On Dec 4, 2006, at 10:13 AM, Sindhi, Abdul Waris wrote:
We are running a CFD application on the Blue Gene that performs
sequential
I/O on all the processors at around the same time. The case we
currently run
is out of user homedir. We are currently running a 40 processor
breakup, and
the read/writes are to a file sized around ~20MB.
The read/write performance looks pathologically slow at around
20-30 times
slower when compared to normal runs. We are wondering if anyone
else has
run into similar issues with slow I/O on the Blue Gene ?
Thanks,
A. Waris Sindhi
High Performance Technical Computing
Pratt & Whitney, UTC
(860)-565-8486
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