Administrator Guide

Performance characterization
34 Dell EMC Ready Solution for HPC PixStor Storage | Document ID
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
Figure 19 Metadata Performance - Small files (4K)
The system gets very good results for Stat and Removal operations reaching their peak value at 256 threads
with 8.2M op/s and 400K op/s respectively. Read operations attained the maximum of 44.8K op/s and Create
operations achieving their peak with 68.1K op/s, both at 512 threads. Stat and Removal operations have more
variability, but once they reach their peak value, performance does not drop below 3M op/s for Stats and
280K op/s for Removal. Create and Read have less variability and keep increasing as the number of threads
grows. As can be observed, the extra drives of the capacity expansions only provide marginal changes in
metadata performance.
Since these numbers are for a metadata module with a single ME4024, performance will increase for each
additional ME4024 arrays, however we cannot just assume a linear increase for each operation. Unless the
whole file fits inside the inode for such file, data targets on the ME4084s will be used to store the 4K files,