Is your Linux server too slow or load is too high? One of the possible causes of such symptoms may be high IO (input/output) waiting time, which basically means that some of your processes need to read or write to a hard drive while it is too slow and not ready yet, serving data for some other processes.

Common practice is to use iostat -x in order to find out which block device (hard drive) is slow, but this information is not always helpful. It could help you much more if you knew which process reads or writes the most data from your slow disk, so you could renice it using ionice or even kill it.

iotop identifies processes that use high amount of input/output requests on your machine. It is similar to the well known top utility, but instead of showing you what consumes CPU the most, it lists processes by their IO usage. Inspired by iotop Python script from Guillaume Chazarain, rewritten in C by Vyacheslav Trushkin and improved by Boian Bonev so it runs without Python at all.

iotop is licensed GPL-2.0+