Interpretation of non-zero vmstat “bi/bo” values

Question

What are useful rule-of-thumbs with regard to interpreting non-zero vmstat "bi/bo" values? When are the values "okay" and when are they an indication of that the system is under heavy stress?

The question is of course hard to answer in the general case, but I'm looking for rule of thumbs rather than exact rules.

Solution 1

It's probably a lot better to run "iostat -x" which will often give a percentage utilization of disk I/O bandwidth for each device.

If you don't have iostat, then I'd run "hdparm -t /dev/sda " in a loop for a while while running vmstat in another window to give you a baseline for what a lot of I/O looks like.

Solution 2

bi and bo represent the data transfers between virtual memory and block devices. It depends on your workload. No rule of thumb exists.