[LAD] [OT] bash vs disk activity

Ross Vandegrift ross at kallisti.us
Thu Oct 11 17:42:22 UTC 2007

On Tue, Oct 09, 2007 at 06:58:40PM +0700, Patrick Shirkey wrote:
> Does anyone have a script for monitoring with iostat or vmstat while in
> async mode?
> I'm thinking a bash equivalent to the disk monitor on gkrellm which
> allows me to know when a transfer has completed.

Something like this will return when five seconds have passed with
no write requests being issues to the device sda:

CURRENT=$(cat /proc/diskstats | grep sda\  | awk '{ print $8 }')
while true; do
	sleep 5
	CURRENT=$(cat /proc/diskstats | grep sda\  | awk '{ print $8 }')
	if [ "$LAST" == "$CURRENT" ]; then

/proc/diskstats lists a few things.  For complete devices (ie,
/dev/sda instead of /dev/sda1), it lists:

Field 1 -- # of reads issued
Field 2 -- # of reads merged, field 6 -- # of writes merged
Field 3 -- # of sectors read
Field 4 -- # of milliseconds spent reading
Field 5 -- # of writes completed
Field 7 -- # of sectors written
Field 8 -- # of milliseconds spent writing
Field 9 -- # of I/Os currently in progress
Field 10 -- # of milliseconds spent doing I/Os
Field 11 -- weighted # of milliseconds spent doing I/Os

Where field n is the nth field after the device name.

Ross Vandegrift
ross at kallisti.us

"The good Christian should beware of mathematicians, and all those who
make empty prophecies. The danger already exists that the mathematicians
have made a covenant with the devil to darken the spirit and to confine
man in the bonds of Hell."
	--St. Augustine, De Genesi ad Litteram, Book II, xviii, 37

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