Seems an idea similar to the IBM POWER8 CAPI Flash solution
The IBM Data Engine for NoSQL, based on POWER8, a PCIe FPGA accelerator from Nallatech that is connected through a coherent interface called CAPI, and the Redis NoSQL database, delivers the same combination of fast DRAM and cheap Flash seen as DRAM. The FPGA maps the Flash as a memory block for the redis database to use, using key value store operations. The CAPI interface allows the accelerator to participate in the coherency domain of the processors - in other words, it can directly access main memory, without requiring system-to-device memory copy that is common in accelerators that are seen as I/O devices.
Since Flash is cheaper than DRAM, you can have lots of memory on small servers at an affordable pricing. The S822L supports two IBM FlashSystem 900 connected as "real memory", for a total of 114 TB of "RAM" - on a 2U system. The Redis SW can mange DRAM and Flash for optimizing response time requirements, and the solution offers an attractive balance between performance, cost, and simplicity.
There is a paper describing CAPI and the NoSQL solution with POWER8 at http://www-03.ibm.com/systems/power/solutions/bigdata-analytics/data-engine-nosql/
Disclaimer: I work for IBM. This comment is my own opinion and may not represent IBM's position or statements.