Administrator Guide

Performance characterization
38 Dell EMC Ready Solution for HPC PixStor Storage | Document ID
Sequential IOR Performance N clients to 1 file
Sequential N clients to a single shared file performance was measured with IOR version 3.3.0, assisted by
OpenMPI v4.0.1 to run the benchmark over the 16 compute nodes. Tests executed varied from a one thread
up to 512 threads since there were not enough cores for 1024 or more threads. This benchmark tests used 8
MiB blocks for optimal performance. The previous performance test section has a more complete explanation
for why that matters.
Data caching effects were minimized by setting the GPFS page pool tunable to 16GiB and the total file size
was twice the total amount of RAM in the clients used. That is, since each client has 128 GiB of RAM, for
threads counts equal or above 16 threads the file size was 4096 GiB, and an equal amount of that total was
divided by the number of threads (the variable $Size below was used to manage that value). For those cases
with less than 16 threads (which implies each thread was running on a different client), the file size was twice
the amount of memory per client used times the number of threads, or in other words, each thread was asked
to use 256 GiB.
The following commands were used to execute the benchmark for writes and reads, where $Threads was the
variable with the number of threads used (1 to 1024 incremented in powers of two), and my_hosts.$Threads
is the corresponding file that allocated each thread on a different node, using round robin to spread them
homogeneously across the 16 compute nodes.
mpirun --allow-run-as-root -np $Threads --hostfile my_hosts.$Threads --mca
btl_openib_allow_ib 1 --mca pml ^ucx --oversubscribe --prefix
/mmfs1/perftest/ompi /mmfs1/perftest/lanl_ior/bin/ior -a POSIX -v -i 1 -d 3 -e -
k -o /mmfs1/perftest/tst.file -w -s 1 -t 8m -b ${Size}G
mpirun --allow-run-as-root -np $Threads --hostfile my_hosts.$Threads --mca
btl_openib_allow_ib 1 --mca pml ^ucx --oversubscribe --prefix
/mmfs1/perftest/ompi /mmfs1/perftest/lanl_ior/bin/ior -a POSIX -v -i 1 -d 3 -e -
k -o /mmfs1/perftest/tst.file -r -s 1 -t 8m -b ${Size}G