New Formula: SnapRAID: Parity redundancy for independant filesystems

_The following description is from the [official homepage](http://snapraid.sourceforge.net/):_

SnapRAID stores redundancy information in the disk array, and it allows recovering from up to two disk failures.

SnapRAID is mainly targeted for a home media center, where you have a lot of big files that rarely change.

Beside the ability to recover from disk failures, the other features of SnapRAID are:

- You can start using SnapRAID with already filled disks.
- The disks of the array can have different sizes.
- You can add disks at any time.
- If you accidentally delete some files in a disk, you can recover them.
- If more than two disks fail, you lose the data only on the failed disks. All the data in the other disks is safe.
- It doesn't lock-in your data. You can stop using SnapRAID at any time without the need to reformat or move data.
- All your data is hashed to ensure data integrity and to avoid silent corruption.