I think Drivepool is great - a year or so ago (after buying and populating a NAS) I realised I had a fair few old, unused hard drives of different ages and sizes. I knew I couldn't best use them in a traditional NAS or RAID array but wondered if there was software available that would let me do something with them. A few minutes searching revealed Drivepool. And in turn that let me utilise the otherwise redundant drives in an equally redundant old PC. I was pretty pleased to have made 7 GB of relatively protected storage -- 3.5 when duplicated. I did some work to my "main" PC this week and decided to pool some drives in that (this time all the same size) and did look at Windows Storage Spaces. But what put me off that was what is, in many ways, Drivepool's biggest advantage over any NAS or RAID solution -- the files can be read off any drive in another PC without much pain. So a system failure needn't involve much work to get to files. That's a huge plus in my book. So now I have two machines running DP and both are going great.