You can always setup a ram disk on your Linux server and then simply have an API that you call that does the writing / reading to and from "disk". Then by simply adding a load-balancer in front of your caching API, you can easily load balance it.
A memory based file system is something which creates a storage area directly in a computers RAM as if it were a partition on a disk drive. As RAM is a volatile type of memory which means when the system is restarted or crashes the file system is lost along with all it’s data.
The major benefit to memory based file systems is that they are very fast – 10s of times faster than modern SSDs. Read and write performance is massively increased for all workload types. These types of fast storage areas are ideally suited for applications which need repetitively small data areas for caching or using as temporary space. As the data is lost when the machine reboots the data must not be precious as even scheduling backups cannot guarantee that all the data will be replicated in the even of a system crash. By storing it in memory / ramdisk, you're effectively doing what Redis / Memcached is already giving you out of the box.