[Hizonner]

Erm. The read head and the write head in a magnetic drive are the same head. You can't keep the head away from the surface if you want to read the disk. But you can disable power to the driver that puts write current into the head.

... and you could absolutely build similar functionality into a flash chip. But most likely you can't actually buy such chips, at least not with any real capacity.

[mypalmike]

There are multi-actuator hard drives out there. I don't know if any of them separate read heads from write heads, but it would certainly seem possible for such a drive to exist.