One of the pioneers in hologram storage was InPhase Technologies which went out of business in 2010 after investing 9 years and about $100 million into research. InPhase couldn't keep up with the year-by-year increases in storage needs and its storage devices could only run about as fast as a thumb drive.

Here's how the company described the hologram recording process:

"Light from a single laser beam is split into two beams, the signal beam (which carries the data) and the reference beam. The hologram is formed where these two beams intersect in the recording medium. The process for encoding data onto the signal beam is accomplished by a device called a spatial light modulator (SLM). The SLM translates the electronic data of 0s and 1s into an optical “checkerboard” pattern of light and dark pixels. The data are arranged in an array or page of over one million bits. The exact number of bits is determined by the pixel count of the SLM."

Credit: InPhase Technologies