I highly recommend iStat Menus / MenuMeters for monitoring. Also if you run "sudo fs_usage" in the Terminal you can see what is accessing the disk. This can ea

I highly recommend iStat Menus / MenuMeters for monitoring. Also if you run "sudo fs_usage" in the Terminal you can see what is accessing the disk. This can easily show what new app you've installed is causing problems. Likewise learn about launchctl/LaunchAgents/LaunchDaemons so you can disable startup daemons. Big tip: Make sure to add to the Spotlight->Privacy section any folders that you don't want indexed e.g. Downloads, Bittorrent Folders, External Drives.