The idea is not that weird. Lots of applications run from RAM most of the time, needing long cache warmups before performing well. If you keep your entire storage in RAM this isn't necessary, and you can do away with the caching layer.
This looks like the "RAM SAN" products, where there's a bunch of memory and some spinning disks with enough local battery backup to flush to disk. I think the main difference is that they want the data aggregated across multiple machines, which I don't think that previous solution had.
