This is perfectly possible. I used to work on something that did just this but at the time used a small battery and an SSD to quickly dump the volatile state before power loss. This meant we had to limit the amount of volatile data that could be stored in ram (due to the transfer rate and up time on the battery). We were eagerly awaiting 3DXP DIMMs so that we could remove that limit. It really will have a big impact on critical systems where any data loss is not acceptable.