Postmark is a benchmark, which test performance of reading and writing to multiple files.
Download the c file and compile it. When running the program you will get a command prompt. From there you can run a few commands to customize the test. By typing help you will get a list of all possible commands. With run you will start the performance test. If you didn't set any options, it will run with default options.
A possible output could look like this:
pm>run Creating files...Done Performing transactions..........Done Deleting files...Done Time: 158 seconds total 66 seconds of transactions (7 per second) Files: 760 created (4 per second) Creation alone: 500 files (5 per second) Mixed with transactions: 260 files (3 per second) 224 read (3 per second) 0 appended (0 per second) 760 deleted (4 per second) Deletion alone: 520 files (86 per second) Mixed with transactions: 240 files (3 per second) Data: 3584.00 megabytes read (22.68 megabytes per second) 12160.00 megabytes written (76.96 megabytes per second) pm>quit