A new feature in Windows 8 is ‘storage spaces’, a kind of software RAID, similar to the drive extender functionality found in the defunct Windows Home Server. Unlike Windows Home Server, however, Windows 8 provides no means of removing hard drives from simple (no resiliency) storage spaces, even when there’s adequate free space. Deleting the storage space will remove all your data, so you’ll need to copy everything to other storage devices first. If all your hard drives are being used by the storage space, this can be tricky.
My home server has recently decided to reset itself at random intervals (no errors to speak of), possibly due to an incompatibility between some piece of hardware and Windows 8 (or possibly just a failing piece of hardware). I’d like to try re-installing Windows 8 to see if that helps, and try Windows 7 if it doesn’t, but first I need to find a way to transfer about 8TB of data from my storage space.
Moral of the story: don’t use simple storage spaces if you ever plan to dismantle them.