The hdparm command is very useful to determine hard disk speeds for ANSYS runs:

  1. Determine the device of interest using the df -h command. For example, if your ANSYS working directory is in /home, determine which device /home is located in, if you’re not already sure. (This is usually something like /dev/sda or /dev/hda.)
  2. Run hdparm -Tt device, where device is the device name found in Step 1 above. If you are not superuser, you will probably need to use sudo, such as sudo hdparm -Tt /dev/sda.  With this command, timings of both cache and device reads will be printed.
  3. You may wish to repeat Step 2 two or three times to get better estimates from hdparm

An example output is shown below:

/dev/sda:
Timing cached reads:   7540 MB in  2.00 seconds = 3773.10 MB/sec
Timing buffered disk reads:  488 MB in  3.01 seconds = 162.13 MB/sec

With this information, we can see that large memory systems are effective in caching files, thus providing better performance.

This is especially important for the sparse direct solver (EQSLV,SPARSE).  After a solution, open the .BCS file in a text editor and search for the following line:

effective I/O rate (MB/sec) for solve   =     2524.122181     2671.123651

This shows the effective I/O rate.  Sparse direct solver scratch files are listed at the very bottom, and although the factorized matrix (.LN09) may be present (usually, written and read 3x total for a single solve), the I/O rate can be very fast if the file can fit in memory.

Note that hdparm can be used not only for timing benchmarks as noted above but also to adjust your hard disk parameters. However, misuse of hdparm can result in data loss or other issues, so be sure to read the man pages carefully first.