Netdata Community



OS: Linux, FreeBSD

This alert presents the average percentage of time the disk was busy over the last 10 minutes.
If you receive this it indicates high disk load and that the disk spent most of the time servicing read or write requests.

This alert is triggered in a warning state when the metric exceeds 98%.

This metric is the same as the %util column on the command iostat -x:

%util is the percentage of the time the drive was doing at least one thing.
Device saturation occurs when this value is close to 100% for devices serving requests serially.
But for devices serving requests in parallel, such as RAID arrays and modern SSDs, this number
does not reflect their performance limits.
As a measure of general IO busyness %util is fairly handy, but as an indication of how much the
system is doing compared to what it can do, it’s terrible.1

References and Sources
  1. Two traps in iostat: %util and svctm

Troubleshooting Section

Check per-process disk usage to find the top consumers

Note: If you got this alert for a device serving requests in parallel, you can ignore it.

Use "iotop" on Linux

iotop is a useful tool, similar to top, used to monitor Disk I/O usage, if you don’t have it,
then install it

root@netdata~ # sudo iotop

Using this, you can see which processes are the main Disk I/O consumers on the IO column.

Use "top" on FreeBSD

You can use top:

root@netdata~ # top -m io -o total

The -m io sets top to display I/O statistics, and the -o total indicates the results will be
ordered according to the field “Total”.