Typically, SSDs use flash as cache memory as opposed to the much faster DRAM, but Buffalo says that MRAM can bridge the gap between NAND flash and DRAM and provide a much better cache solution as a result.
Flash is used today as it has non-volatile properties and does not lose its content like DRAM when the power is cut off. MRAM, which is similar to DRAM structure, is also a non-volatile memory technology, but faster than flash. The technology has been in development for more than a decade. In the 2005 time frame, MRAM was believed to have an opportunity to succeed flash as a mass-market solid state memory technology, but has been held back by low density and, as a result, high cost.
In the Buffalo device, however, the SSD uses 4 GB of NAND flash storage and just 8 MB of MRAM cache, which makes the use of MRAM a much more compelling proposition. It's not a consumer device either as the SSD will be targeted at extreme industrial applications and for integration in machinery that runs at up to 85 degrees Celsius. Buffalo states that the use of MRAM makes its SSD more reliable overall and reduces power consumption as well. However, we know that new technologies and expensive ideas tend to trickle down from the high-end if they make sense. It's not entirely unreasonable to foresee an MRAM SSD for the consumer market at some point in the future.