I’m a big fan of Linux tools which allow you to monitor things in great detail. Some of my favorites are strace, the systemtap tools, and sysstat. Finding tools similar to these on a Mac is a little more difficult. There’s a great blog post from Brendan Gregg’s blog that covers a lot of detail around dtrace and its related tools: http://dtrace.org/blogs/brendan/2011/10/10/top-10-dtrace-scripts-for-mac-os-x/ One of the handier tools is iosnoop.