In my fantasies I visualize data storage in a piece of crystal the size of a sugar cube, containing petabytes* of data, addressed/accessed by three tiny lasers at mutual right angles. Data transfer speed limited by speed of light considerations.

tanstaafl.

*Megabyte = 2^20 bytes
*Gigabyte = 2^30 bytes
*Terabyte = 2^40 bytes
*Petabyte = 2^50 bytes
*Exabyte. = 2^60 bytes