It's possible thanks to the magic of dtrace. In a storage appliance, you wouldn't expect the load to be overwhelmingly CPU bound[1], so performing real time in

It's possible thanks to the magic of dtrace. In a storage appliance, you wouldn't expect the load to be overwhelmingly CPU bound[1], so performing real time instrumentation isn't a noticeable performance hit: http://www.solarisinternals.com/wiki/index.php/DTrace_Topics_Overhead http://www.solarisinternals.com/wiki/index.php/DTrace_Topics... [1]: assuming you aren't using ZFS gzip compression: http://blogs.smugmug.com/don/2008/10/13/zfs-mysqlinnodb-compression-update/ http://blogs.smugmug.com/don/2008/10/13/zfs-mysqlinnodb-comp...