Well if it is up to VMware founder Mendel Rosenblum the answer is DRAM.
The Project "RamClouds- Scalable High Performance storage Entirely in DRAM" sounds very interesting.
Find out more about the project here: http://www.stanford.edu/~ouster/cgi-bin/projects.php
The paper "The Case for RAMClouds: Scalable High-Performance Storage Entirely in DRAM" can be downloaded from this location.
Original posting and Discussion: http://www.ntpro.nl/blog/archives/1663-Hey-Drummonds-forget-SSD-RAM-is-the-future.html
The solution: one possible solution is to shift the home of online data from disk to DRAM. A RAMCloud is a new class of storage intended for datacenters, where all information lives at all times in fast DRAM. Large-scale systems are created by aggregating the main memories of thousands of commodity servers. RAMClouds are interesting because they combine large scale (100-1000 TBytes) with 100-1000x faster latency than current systems (5-10 microseconds to access small amounts of RAMCloud data from application servers in the same datacenter). In addition to simplifying the creation of large-scale Web applications, we believe that RAMClouds may enable a new breed of data-intensive applications.
A product available now RAMSAN: http://www.ramsan.com/products/4
The RamSan-440 is a new solid state disk with record high performance, record high capacity for a RAM-based system, and a combination of features that help ensure the highest availability of data to its users. The RamSan-440 is the world's first non-volatile RAM-based SSD to sustain 600,000 IOPS (input/outputs per second) and deliver 512GB of storage capacity in a 4U rack-mount chassis. It's also the first SSD to use RAIDed NAND Flash storage modules for data backup, and the first system to incorporate Texas Memory Systems' patented IO2 (Instant-On Input-Output) technology