fastest raw device copy?

[Wojciech Puchar]

> In general, what you're doing is correct for a block copy.  There is
> nothing (that I know of) which is faster; you're copying 500GB of data
> (including the unused portion -- you *did* ask for a block copy),
> and this takes a long time.  Be patient.
>
> On the flip side, your blocksize (bs) there is quite high for no good
> reason.  I'd pick something more like bs=64k or bs=128k.  The default
> (512) is too small for what you want, but 10MBytes is silly.

should be big but less than drive's buffer, and be multiply of sector 
size.