Question
How can I use the iotop utility to find processes that contribute to high disk usage?
Note: When diagnosing high IO resource usage issues, there is always the possibility of disk or filesystem corruption as being the cause. In those cases, you may find that there are no processes doing large amounts of IO, yet the IO usage is reported as being very high. You can learn how to diagnose disk or filesystem corruption issues with the resources at the end of this article.
CPANEL_WARN: The investigation, diagnoses, and resolution of problems related to resource usage are tasks that are best handled by a systems administrator with the skills, training, and expertise required to do so effectively.
Answer
- Login to the server via SSH or Terminal as the
rootuser -
Use the following command to review the recent %IOWait on the server
# sar
- If you see that there is a recent and sustained pattern of IOWait above 0, or especially above %5, there is a good chance that whatever is causing the elevated IO resource usage is currently active on the server.
-
If you believe that the IO usage is currently happening, issue the following command
# iotop -aoP
-
The output will reveal processes that perform reads and writes to disk. Generally, the more time a processes spends performing disk reads or writes, the higher it will be on the list. However, processes may also perform bursts of high usage in the MB or GB range, so watching the READ and WRITE columns is also important.
Note: Servers using EXT 3 and 4 file systems may show journal processes using a lot of resources. While these are a problem, they are usually indicative of other processes doing the actual resource usage.
Additional Information
How to diagnose high IO and high load with iotop
What is IOWait in relation to the sar command, and when should I be concerned?
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