Well, it's not really shfs, though kind of odd they named it that. The mount flags don't really give any clues, but it is a FUSE filesystem, and what it does is extremely similar to what mhddfs does.

What they seem to do underneath, is simply a drive/sector level parity sum across all data drives. It's not a "file level" parity, but a sector level parity.

That latter part is very handy -- RAID layers do that too, but then they also force striping upon us. This unRAID just does the parity, without the striping. End of Story.

The reason for the sucky perfomance is partly because they're using FUSE rather than an in-kernel solution, so it's going to be CPU heavy as well as incur lots of read latency, just like mhddfs and for the same reasons. Writes will be much slower, because of the read/modify/write required for parity updates.

But some of the performance loss you see could simply be due to not having correctly tuned Samba for MS-Win accesses. Didn't we have a thread on that here recently?

Cheers!