On Fri, Apr 20, 2012 at 12:42 AM, Lists <lists at benjamindsmith.com> wrote: > Problem as follows: > > 1) Plug in an external USB drive. > > 2) Mount it anywhere. Doesn't matter how. > > 3) Copy a few GB of data to the drive from a non-USB disk. > > 4) Watch the load average "climb" to 5.x, sometimes 10.x or more. Why? > This on an otherwise unloaded system. Doesn't matter how many cores, how > much RAM, 32/64 bit, etc. > > Why should copying some files to a USB drive cause load averages to > climb so high? (and network monitors to freak out?) The CPU has to do the work of the transfer over usb - which is why it is cheap. Real disk controllers use DMA without a lot of CPU involvement. -- Les Mikesell lesmikesell at gmail.com