Quick'n dirty (remote) disk troughput measurement

  toucheatout  2006-08-07 11:53  Linux  

There are good tools to very closely evaluate a disk or disk array performance. This is especially critical for remotely mounted filesystems, where performance tweaks can turn a shame into a very reasonable and efficient network attached storage.
Bear in mind that it is difficult to take into account the multitude of requests when testing alone, and thoroughly tested system can behave very differently under a load from different sources.

Testing Writes

Replace the bs (as Block Size) by the setting you want to test, then ajust the count to create a file of the size you chose. Try to make it quite (2x) bigger than memory on the server if you are to test reading afterwards. /dev/zero is a good source of quickly grabbed bits...


time dd if=/dev/zero of=/mnt/test bs=16k count=16384


This creates a 256Mb file and outputs the time it took (look at the "real" line to get the time it took from an user perspective).

The other end of the rope: testing reads

Try then to read it and measure the read performance (command-line, filesystem is supposed mounted on /mnt)


time dd if=/mnt/test of=/dev/null bs=16k


Those steps should be each carried out several (at least 3) times under absence of activity, and the results averaged.