In the current version of WHS (I can't speak for the upcoming "Vail" release) you can think about its redundancy in terms of file-level software RAID 1 without

In the current version of WHS (I can't speak for the upcoming "Vail" release) you can think about its redundancy in terms of file-level software RAID 1 without integrity checking. Pros and cons abound in that setup, of course, but setting aside the lack of integrity checking ala ZFS for a moment, I have personally taken advantage of the file-level software RAID 1 portion when my first WHS server encountered an internal hardware issue and I had to pull its drives (normal NTFS drives full of the files) and bring them online in a replacement WHS server. Each drive was brought online out of the storage pool, its files copied into the pool volumes, and finally the drive was added to the storage pool. It requires an extra drive already in the pool to pull this off, but given that it worked very well, far better than some of the horror stories I've heard about people trying to transplant RAID 5 and 6 setups when other NAS solutions have failed at the server level. A part of me of course wishes for a ZFS-style WHS, and perhaps MSFT will get there some day, but in the meantime I can certainly see how WHS's design decisions were reached.