MDTest is a synthetic MPI parallel benchmark for testing the metadata performance of filesystems. Each thread operates on its own working set.

The benchmark operates in phases (excerpt):

• Creation of directories
• Creation of files
• Reading files
• Deletion of files
• Deletion of the tree

Here are a few important command line arguments:

• -d Target directory to run the test on
• -i Iterations, the benchmark is repeated this number of times to investigate standard deviation
• -z Depth of the hierarchical directory structure
• -b Branching factor, how many directories to create, used in conjunction with -z
• -I Number of files to create per directory
• -w Write this number of bytes to each file after it is created
• -e Read this number of bytes from each file in the read phase

To print the internal operations of the benchmark for rank 0 add the option -V3.

For example runnning mpiexec -n 2 ./mdtest -d /tmp/ -b 10 -z 2 -i 1 -I 100 (using mdtest version 1.9.3) results in the following output

-- started at 12/02/2016 11:24:25 --

mdtest-1.9.3 was launched with 2 total task(s) on 1 node(s)
Command line used: ./mdtest -d /tmp/ -b 10 -z 2 -i 1 -I 100
Path: /tmp
FS: 15.6 GiB   Used FS: 0.0%   Inodes: 3.9 Mi   Used Inodes: 0.0%

2 tasks, 22200 files/directories

SUMMARY: (of 1 iterations)
   Operation                      Max            Min           Mean        Std Dev
   ---------                      ---            ---           ----        -------
   Directory creation:     980917.027     980917.027     980917.027          0.000
   Directory stat    :    1509378.324    1509378.324    1509378.324          0.000
   Directory removal :    1065726.028    1065726.028    1065726.028          0.000
   File creation     :     845203.634     845203.634     845203.634          0.000
   File stat         :    1563488.352    1563488.352    1563488.352          0.000
   File read         :    1064592.847    1064592.847    1064592.847          0.000
   File removal      :    1214044.210    1214044.210    1214044.210          0.000
   Tree creation     :     734333.981     734333.981     734333.981          0.000
   Tree removal      :     860568.843     860568.843     860568.843          0.000
   
-- finished at 12/02/2016 11:24:25 --

• CPU: Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
• HDD: HGST HTS721010A9 A3P0

$ mpiexec -n 8 ./mdtest -z 1 -L -u -n -N 1 -b 10 -d /hdd/local/benchmark/ -I 1000 -w 3900 -e 3900

-- started at 12/02/2016 15:35:49 --

mdtest-1.9.3 was launched with 8 total task(s) on 1 node(s)
Command line used: ./mdtest -z 1 -L -u -n -N 1 -b 10 -d /hdd/local/benchmark/ -I 1000 -w 3900 -e 3900
Path: /hdd/local/benchmark
FS: 916.8 GiB   Used FS: 17.1%   Inodes: 58.2 Mi   Used Inodes: 0.8%

8 tasks, 88000 files/directories

SUMMARY: (of 1 iterations)
   Operation                      Max            Min           Mean        Std Dev
   ---------                      ---            ---           ----        -------
   Directory creation:       6927.308       6927.308       6927.308          0.000
   Directory stat    :    4238519.464    4238519.464    4238519.464          0.000
   Directory removal :     730975.466     730975.466     730975.466          0.000
   File creation     :      48177.549      48177.549      48177.549          0.000
   File stat         :    3944079.074    3944079.074    3944079.074          0.000
   File read         :    1853445.039    1853445.039    1853445.039          0.000
   File removal      :     977343.745     977343.745     977343.745          0.000
   Tree creation     :      98373.868      98373.868      98373.868          0.000
   Tree removal      :        569.562        569.562        569.562          0.000

-- finished at 12/02/2016 15:36:04 --

Here is a longer run: $ mpiexec -n 8 ./mdtest -z 1 -L -b 10 -d /hdd/local/benchmark/ -I 10000 -w 3900 -e 3900

-- started at 12/02/2016 15:55:59 --

mdtest-1.9.3 was launched with 8 total task(s) on 1 node(s)
Command line used: ./mdtest -z 1 -L -b 10 -d /hdd/local/benchmark/ -I 10000 -w 3900 -e 3900
Path: /hdd/local/benchmark
FS: 916.8 GiB   Used FS: 17.1%   Inodes: 58.2 Mi   Used Inodes: 0.8%

8 tasks, 880000 files/directories
                                                                                         
mpiexec -n 8 ./mdtest -z 1 -L -b 10 -d /hdd/local/benchmark/ -I 30000 -w 3900 -e 3900

SUMMARY: (of 1 iterations)
   Operation                      Max            Min           Mean        Std Dev
   ---------                      ---            ---           ----        -------
   Directory creation:       5027.549       5027.549       5027.549          0.000
   Directory stat    :    4453443.823    4453443.823    4453443.823          0.000
   Directory removal :       9901.782       9901.782       9901.782          0.000
   File creation     :      23445.425      23445.425      23445.425          0.000
   File stat         :    2970635.216    2970635.216    2970635.216          0.000
   File read         :      55775.043      55775.043      55775.043          0.000
   File removal      :      22110.331      22110.331      22110.331          0.000
   Tree creation     :      90112.000      90112.000      90112.000          0.000
   Tree removal      :         25.082         25.082         25.082          0.000

-- finished at 12/02/2016 16:01:57 --