Generating an I/O trace.

[Christof Schoeman]

Hi there

I want to generate an I/O trace on a Tru64 system. That is, each and every I/O to disk should be logged in the trace file. Not at the volume or file system level, but at the device driver level.

Where do I start?

[Ivan Ferreira]

Have you tried collect? See man collect to know how to activate at boot time. Logging will be generated in /var/adm/collect.dated, use collect -p (playback) -sd (subsistem disk) to view the collected data.

[Hein van den Heuvel]

Best I know this does not existunder Tru64 at the disk level.
Are you aware of a tool on an other Unix that can do this job?

The closest you can get for this is to use LSM voltrace.
http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/V50_HTML/MAN/MAN8/0479____.HTM

What problem are you really trying to solve?
Performance?
Data Corruption?


fwiw,
Hein.

[Venkatesh BL]

'collect' provides disk IO info on the system-level. But, I guess you are looking for something that would provide the info on the file or process level. If so, I don't think 'collect' would be useful.

[Christof Schoeman]

Hi

I want to collect the I/O traces to do statistical analysis on them, for research purposes. Stuff like inter-arrival times, mean size, mean distance and degree of parallalism are the kind of things I'm looking for.

For that, I need to tap in at the device driver somehow, to collect some information for each and every I/O.

The guys at HP research labs did this before on HP-UX, by what means, I don't know. This is what they had to say...

"All of our data were obtained using a kernel-level trace facility built into HP-UX. The tracing is completely transparent to the users..."

Also don't think collect will do it, perhaps the table() function can help. Let me see.