This is a simple tool (and munin plugin) to measure HDD latency with high accuracy.

Features:

• Direct I/O to bypass any caching (only on Linux (?))
• clock_gettime(CLOCK_MONOTONIC, ...) for nano-second accuracy (depending on platform)
• munin compatible output
• no external dependencies

Pretty simple stuff:

• The tool sets up and aligns a hardcoded 1MB buffer
• measures the current timestamp as described by clock_gettime(CLOCK_MONOTONIC, ...)
  • creates & opens a file for direct I/O
  • writes the buffer & closes the file
• creates a second timestamp and displays the difference between the two (the elapsed time)

ioping.c offers minimal configuration using the #define's at the beginning of the file.

#define NUM_IOPING_RUNS 3 // number of times ioping writes to disk, results will be averaged
#define SLEEP_BETWEEN_RUNS 1 // in seconds
#define PING_PATH "/var/tmp/test.ping" // file path to write to

Using /tmp for PING_PATH is discouraged since some servers mount a ramdisk/tmpfs on that path.

I personally use CMake but you are free to use your own build system or directly invoke gcc:

mkdir build
cmake ..
make
# run with:
./ioping

Simply drop the binary in your plugins directory and restart munin-node:

cp -v ioping /etc/munin/plugins/
systemctl restart munin-node