z'mIO is mainly a block device benchmark with emphasis on asynchronous I/O in
the linux kernel. The benchmark also works on regular files.

The linux libaio API is used instead of the POSIX aio interface due to the low
queue depths of the linux POSIX aio implementation.

If you don't have the libaio header files installed, you should put libaio.h
in the benchmark directory and execute:
make nompi_nolibaio

For more information execute:
./zmIO --help

--------------------------------------------------------------------------------

Usage: z'mIO -- Raw device Benchmark

options:
 --system  filename: System's configuration file
 --sequent "f:no/"|operations|"unit:B": Sequential access pattern
 --strided "f:no/"|operations|"unit:B": Strided access pattern
 --random  "f:no/"|operations|"unit:B": Random  access pattern
   A pattern has frequency no% [1,100], request size B bytes.
   Operations are defined per pattern and are:
   r=read, w=write, rw=read-write, rr=re-read, ww=re-write
   operations="r:no/w:no/rw:no/rr:no/ww:no": frequency no% [1, 100]
 --time    value: Time limit of benchmark's execution in seconds
 --io_out  value: Number of I/O outstanding requests
 --direct  value: Direct I/O (0: not set / 1:set)
 --sync    value: Synchronous I/O (0: not set / 1:set)
 --file    value: File I/O instead of block device I/O (0: not set / 1:set)
 --touch   value: Touch data-buffer at every I/O (0: not set / 1:set)
 --help: Print options usage and exit

The system configuration file has one line per thread accessing a device/file:
hostname.mydomain.com filename

===============================================================================
                                  Example
===============================================================================
System configuration file with name myconf and contents:
 localhost /dev/sda

Command line with parameters:
 ./zmIO --system myconf --sequent "f:50/r:100/unit:65536" --random "f:50/r:30/w:70/unit:4096" --direct 1 --time 30 --io_out 64

In this run, one thread opens block device /dev/sda for direct I/O.
Total run time of the experiment is 30 seconds.
There are at most 64 outstanding I/Os in the device queue.
There is 50% chance for an operation to be either sequential or random.
In the sequential case streaming reads of 64KB are performed.
In the random case, there is 30% reads and 70% writes for 4KB accesses.