dd performance on Mac OS X vs. Linux

For OS X, use /dev/rdisk3.

For some reason rdisk is faster than disk. I believe it has to do with buffers.

Also in general using the bs flag with dd helps with speed.

dd if=/path/to/image.iso of=/dev/sdc bs=1M

The bytesize is 1M which transfers faster. On OS X you have to use 1m (lowercase) instead of 1M.