On Tue, Jan 15, 2013 at 04:34:50PM -0500, Bradley C. Kuszmaul wrote: > So does it cost a lot to read all the extents just to read the first block? Depends on the number of extents in the file. Figure an IO per 250 extents for a 4k block size filesystem (extent records are 16 bytes in size on disk). Cheers, Dave. -- Dave Chinner david at fromorbit.com