The description of poolIt - Play With New Friends
poolIt brings affordable storage virtualization by allowing you to unite multiple volumes (hard drives, USB or FireWire devices, network shares) into a storage pool. The pool mounts on your computer as a local drive at a desired mount point and its size equals the sum of the sizes of the devices added to it.
With poolIt you can dynamically add/remove volumes from the pool without any data loss. Volumes can contain data prior to adding them to the pool. When adding a volume to the pool, all existing files and folder structures are merged, and exposed in the resulting virtual volume while the original drives are hidden. When removing a volume from the pool, the data it contains remains intact and accessible.