Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I want to know about how to view the disk I/O in linux so that i can check if i have to increase the ram.

Also the limits/thresholds after which i should increase the ram.

Thank You

share|improve this question
up vote 4 down vote accepted

If you have kernel ≥ 2.6.20 with the TASK_DELAY_ACCT and TASK_IO_ACCOUNTING options enabled, i suggest iotop.

top like realtime display of system io. Great tool. iotop homepage

share|improve this answer

Trending I/O can be done using something similar to iostat or sar (which is provided under the sysstat package under debian)

As to the limits/thresholds after which you should increase the amount of RAM it really depends on your machine and what you consider to be acceptable service levels.

Personally, I would be looking at the %iowait figure. Anything higher than about 5% is where you're likely to start seeing performance degradation.

From here you need to start looking at read/write trends. Keep in mind, if you're write bound then increasing the amount of RAM may NOT have any effect on performance.


share|improve this answer

Try iostat. In Gentoo it's in app-admin/sysstat

share|improve this answer
dstat -D total
iostat -d 2
vmstat -d 2
share|improve this answer

if it's typical server case - install munin to see how load / io activity changes during the day / week. especially linux_diskstats_ is useful for analyzing your io bottlenecks.

share|improve this answer

try iostat -dkx 2

share|improve this answer

Ummm... you should use something like "free -m" to see how much RAM has been used. Once you start hitting swap space is when you should think about increasing it.

You can use "vmstat -n 2" to view disk I/O. For both commands have a read through the man pages to see how they work.

share|improve this answer
Can you explain in detail bi and bo – Muahmmad Zeeshan Nov 23 '09 at 9:11

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.