What is High IOwait on Linux

Updated: Feb 2

Linux high IOwait is a common Linux performance issue. Today we will look at what iowait means and what contributes to this problem. Hope this can give you more ideas about high IOwait issue.

High IOwait on Linux

The iowait column on top command output shows the percentage of time that the processor was waiting for I/O to complete. It indicates that the system is waiting on disk or network IO. Because the system is waiting on those resources, it can not fully utilize the CPU.

The process will get "stuck" in D state because of disk io or NFS io. Processes accessing hard NFS mounts will also be put into D state while they wait for the I/O to return - thus a hard NFS mount from a machine that has dropped off of the network can cause processes to go into D state.

High IOWait usually means that your disk subsystem or network storage is overworked.This can occur due to hardware problems (the kernel is waiting for something from a device that never comes) or from kernel-related issues (driver bugs that cause a system call to never return).

Related Post:

Troubleshoot high iowait issue on Linux

Linux File System: Raw IO and Direct IO

NFS is related to iowait


Join our mail group. Get a free Linux account on Cloud.

Never miss a post!

Want a free Linux account?  This account can be used to login to our cloud server and practice Linux commands.


✔ Linux Commands   ✔ Linux Skills    ✔ LinuxPerformance   ✔ Linux Interview

Some articles are from the public internet. If you find your article misused or undesired here and you don't want us to display it, please let us know and we'll remove it immediately.