[Discuss] RAID question

[Patrick]

Hi.  :-)

Does anyone know if there's a Linux utility for drive cloning,
which compares two drives and *only* writes changes to the
destination drive where it finds differences?  Using dd would
also work, but would end up doing a lot of unnecessary work in
the process [and performing a lot of unnecessary writes].

I had this idea to build a hardware RAID 1+0 array using SD
cards and some junk off eBay, but maintaining it if/when a card
fails could get interesting...  It would also be convenient if
I could remove a single RAID 0 drive, use it for a while, then
reintroduce it [with changes] to the mirrored 1+0 array.
 

Thanks,
Patrick.
-- 
"Never underestimate the bandwidth of a station wagon
 full of tapes hurling down the highway."
		-- Andrew S. Tannenbaum