Administrator Guide

Performance characterization
25 Dell EMC Ready Solution for HPC PixStor Storage | Document ID
Figure 12 Metadata Performance - Empty Files
First, notice that the scale chosen was logarithmic with base 10, to allow comparing operations that have
differences several orders of magnitude; otherwise some of the operations would look like a flat line close to 0
on a normal graph. A log graph with base 2 could be more appropriate, since the number of threads are
increased in powers of 2, but the graph would look pretty similar, and people tend to handle and remember
better numbers based on powers of 10.
The system gets very good results with Stat and Read operations reaching their peak value at 64 threads with
11.2M op/s and 4.8M op/s respectively. Removal operations attained the maximum of 169.4K op/s at 16
threads and Create operations achieving their peak at 512 threads with 194.2K op/s. Stat and Read
operations have more variability, but once they reach their peak value, performance does not drop below 3M
op/s for Stats and 2M op/s for Reads. Create and Removal are more stable once their reach a plateau and
remain above 140K op/s for Removal and 120K op/s for Create.
Metadata performance with MDtest using 4 KiB files
This test is almost exactly identical to the previous one, except that instead of empty files, small files of 4KiB
were used.
The following command was used to execute the benchmark, where Threads was the variable with the
number of threads used (1 to 512 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 --prefix
/mmfs1/perftest/ompi --mca btl_openib_allow_ib 1
/mmfs1/perftest/lanl_ior/bin/mdtest -v -d /mmfs1/perftest/ -i 1 -b $Directories
-z 1 -L -I 1024 -y -u -t -F -w 4K -e 4K