This has been just around the corner for several years, but in 2009 it may finally come to market from InPhase Technologies. Three-dimensional holographic images store more information in less space by recording not only on the surface of the storage medium, as do other technologies, but also within an entire volume of space in the medium. (Technically speaking, we should properly measure holographic storage density in units of bits per cubic inch, but that's not yet a common usage.)
Holograms are created by splitting a single laser light into two beams: One is a reference and another carries the signal. Where the reference beam and the data-carrying signal intersect, the interference patterns are recorded in a light-sensitive storage medium. (Initially, this physical storage device will be a DVD-size disk.) Because multiple beams can be used at different angles, hundreds of unique holograms can be recorded in the same volume of material. In one sense, this is similar to a dual-layer DVD, except that it contains hundreds of layers, each recorded at a different angle so that they are not parallel to one another. The stored information is reconstructed by deflecting the reference beam off the hologram and projecting it onto a detector that reads an entire data page (more than 1 million bits) at once.
The first commercial units are expected to use disks with a capacity of 300GB. A real advantage of holographic storage is that its transfer speed (160MB/sec.) is far higher than the speeds other optical media can deliver.
These use on-chip RAM or flash memory that emulates a hard drive. With no moving parts, solid-state drives are silent and sturdy. With no mechanical delays, they usually provide fast access time and low latency.
StorageTek developed the first modern SSD in 1978. M-Systems (now owned by SanDisk) introduced keychain-size, flash-based solid-state drives in 1995; these are now used successfully as replacements for hard disk drives, and as convenient backup and data-transfer devices (often called thumb drives).
These days, smaller SSDs are commonly found in mainstream consumer netbooks and subnotebooks, while SSDs capable of holding 100GB or more are available at high prices.