[mpich-discuss] Single node IO Aggregator setup
robl at mcs.anl.gov
Tue Jun 21 13:08:20 CDT 2016
On 06/21/2016 12:48 PM, Jon Povich wrote:
> I'm trying to simulate a cluster setup where only the I/O aggregators
> have access to the working directory. Is this feasible to do with romio
> A) Work dir is on Node0's local hard drive.
> B) Remote Node1 has no access to Node0's hard drive
> C) Run a case where only rank 0 on Node0 serves as the I/O aggregator
that should work as long as you only use collective operations. You'll
trigger the "deferred open" optimization.
Your hints are close.
> MPI_Info_set(info, "cb_nodes", "1");
> MPI_Info_set(info, "no_indep_rw", "true");
The hint is actually "romio_no_indep_rw". Where did you find
"no_indep_rw" documented? I'd like to get that fixed.
I'd adjust one more hint: the "cb_config_list" hint. By default it is
"*:1", which means select one MPI process from each node to act as
aggregator. That's *probably* node0/crane/whatever, but you can ensure
the desired node is selected by being more explicit.
I'd make your cb_config_list look like "crane:1" or "node0:1" or
whatever MPI_Get_processor_name returns.
In 2014 we went on a deferred open cleanup and fixed a few bugs. I hope
you are using MPICH-3.1.3 or newer.
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