Hello I have read that under Solaris one can use DTrace to get I/O request size distribution on a global scale (also on a per process/pid basis). See for example http://prefetch.net/articles/observeiodtk.html Can anyone recommend an alternative to get similar information under CentOS? I looked into dtrace for linux but it seems still work in progress, even putting aside CDDL issues ... http://www.crisp.demon.co.uk/tools.html Thanks! Antonello