Your Linode, linodeXXXXX, has exceeded the notification threshold (1000) for disk io rate by averaging 1079.99 for the last 2 hours.
That's what I've been getting in my email for the past week, about 2-3 a day. I tried a few solutions, including finding other ServerFault posts on this issue, but they are not helping.
For example, I tried:
watch -n 1 "(ps aux | awk '\$8 ~ /D/ { print \$0 }')"
At various intervals, this will populate with an nginx process, or a kjournald process, etc but only for a few seconds. So it doesn't really help in figuring out what's causing it, it just tells me I keep getting high i/o.
Thus, the question becomes How can I identify what is causing this high i/o usage? Ideally, without starting at a process list for 6 hours.