Linux Block Tracing

blktrace let's you see detailed information about I/O traffic on a disk devices.

You need to have a 2.6.17-rc1 or newer kernel with "Block io tracing" and debugfs enabled in kernel to use blktrace command.


You can download and install blkrace from http://brick.kernel.dk/snaps/ site or if you use ubuntu you can install it with apt-get.
on ubuntu:

$ sudo apt-get install blktrace


blktrace requires debugfs to run. run mount command to see if it's mounted.
If you can't see debugfs in mount command output for example create a directory called /debugfs and mount it by following command as root

# mount -t debugfs none /debugfs

now you can run blkrace command.


blktrace -r /debugfs/ -d /dev/sda -o - | blkparse -i -

default format of blkparse output is as follows (you can change output format if you like with -f option):





by this way you can get detailed information about ongoing disk activity on your system.

Description of Events:

A IO was remapped to a different device

B IO bounced

C IO completion

D IO issued to driver

F IO front merged with request on queue

G Get request

I IO inserted onto request queue

M IO back merged with request on queue

P Plug request

Q IO handled by request queue code

S Sleep request

T Unplug due to timeout

U Unplug request

X Split