Thanks for all the suggestions. I had a look at systemtap but I have the feeling that in it's current state it is aimed more at kernel developers rather than average admins like me :-) Still, I'll keep an eye on it also give the fact that there seem to be now new documentation being written about it http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/pdf/SystemTap_Beginners_Guide/SystemTap_Beginners_Guide.pdf On the other end, I have discovered blktrace and related tools, and this seems more palatable to me (subjective, I know ...). This example in particular seems to work for me # blktrace /dev/sda -a issue -a complete -w 60 -o - | blkiomon -I 4 -h - thought to share in case anyone finds it useful. cheers A.