Yeah, I've read about that but I couldn't buy it because you could achieve similar results with LVM, ZFS etc. albeit with a bit more thought. For example I used to have a mirror (RAID1) comprised of 1TB, 3TB, 4TB and an 8TB disks. The 1, 3 and 4TB disks were concatenated in an 8TB linear volume (JBOD) and then that was mirrored with the 8TB disk (RAID1). All using standard battle tested software - LVM, mdraid and Ext4. I got 8TB usable from it. I'd have gotten the same in Unraid. The redundancy was equivalent too. With ZFS things are even simpler. Build whatever redundant scheme you have disks for. Use whatever redundancy scheme makes sense for those disks. You could combine multiple schemes. E.g. 1TB + 1TB mirror and a RAIDz1 with 3x 3TB disks, all adding to 7TB of nice contiguous usable space with all the data integrity guarantees of ZFS. Heck if you need to do some 3-disks-in-a-trenchcoat trickery to utilize your obsolete hardware like I did, you can use LVM for that and give it to ZFS to use. When you're ready to expand, buy disks for whatever redundancy scheme you like and just add it to your ZFS pool. No fuss. You like living dangerously? Add disks without redundancy. Can't afford redundancy now but you'd like it later? Add disks without redundancy now, add redundancy later.