1

On my Raspbian 8 (Jessie) system

iostat -dzp 5 |grep -v "k0 "

shows me

:
Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
mmcblk0p2         0.80         0.00         3.20          0         16
Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
:

while

sudo iotop -btoqqqd 5

does not show anything at the same time. Why?

It seems like this problem has been seen before: iotop does not show writes.

I have reported this as bug to Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=856186.

migrated from serverfault.com Feb 26 '17 at 9:17

This question came from our site for system and network administrators.

1

iotop is obviously missing the I/Os for some reason.

If your kernel has ftrace enabled, I would recommend using Brendan Gregg's iosnoop port to Linux ftrace available here to figure out what is responsible for the writes.

  • Thanks, it seems to be a powerful tool. However it doesn't seem to show activity if add lines to a file with date >>test. So I am still missing I/O. – Frank Breitling Feb 26 '17 at 10:56
0

One possible explanation given in the discussion of the bug report is that

  • The processes that are doing writes disappearing before the timer.

This makes sense. Whether this is the expected behavior is under discussion.

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