According to the rasbery pi documentation, You can load your OS to a flash card with either /dev/disk or /dev/rdisk. rdisk stands for raw disk. /dev/disk is a block level device, why would rdisk be 20 times faster? Using Mac OSX Note: In OS X each disk may have two path references in /dev: /dev/disk# is a buffered device, which means any data being sent undergoes extra processing. /dev/rdisk# is a