UPDATE: Looks like someone did fork this and run with it - check out https://github.com/simphax/PoolFS :)
An experimental MacFUSE filesystem featuring pooled storage and per-directory redundancy
UNFINISHED CODE!!!
I really wanted a simple, pooled storage mechanism to run on OS X. I made some progress working on top of MacFUSE - in terms of read-only the pooling mostly worked.
Work to support writing to the pool was underway when the project stalled. The uncertainty of the future of FUSE on Mac contributed to the project fizzling out.
Feel free to fork and carry on :)