How to identify I/O bottlenecks on a Linux server?

Question

How do you determine that the performance of your Linux server is I/O bound and, perhaps more importantly, what process or processes are casuing the problem?

Solution 1

I wrote a comprehensive guide to tracking down performance bottlenecks on Linux systems for work: http://web.archive.org/web/20101028025942/https://anchor.com.au/hosting/development/HuntingThePerformanceWumpus . Covers more than you asked for, but it'll (hopefully) help you track down the problem you're seeing regardless of the actual source.

Solution 2

Top has a field called "iowait". If your system is seeing a lot of that, you know something's up. There's also iotop!

Package: iotop:
Description: simple top-like I/O monitor
 iotop does for I/O usage what top(1) does for CPU usage. It watches I/O
 usage information output by the Linux kernel (requires 2.6.20 or later)
 and displays a table of current I/O usage by processes on the system.
 Handy for answering the question "Why is my disk churning so much?".
Homepage: http://guichaz.free.fr/iotop/

Solution 3

IoTop is probably what you're looking for.

Comments

[Admin]

duplicate of serverfault.com/questions/9428/…

[womble]

Yeah, it's a bit wordy, I'm sure plenty of people have gone "TL;DR" at it. I prefer to give people the tools to solve problems generally rather than give pat answers to specific instances of problems, which leaves them dependent. This stuff is Hard, though, and if tracking down a performance problem isn't what you want to spend your time doing, well, you can always hire someone who's already read the article... <grin>

[John Gardeniers]

That's far too vague to be an answer. How about at least listing some of those commands.

[Michael Hampton]

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.

[womble]

Fixed the link good and proper now. Marketing don't understand the concept of "stable links"...