right now on Wikipedia, it says RAID 1 (Mirroring) has a space efficiency of 1/n, and
Space efficiency is given as the amount of storage space available in an array of n disks, in multiples of the capacity of a single drive. For example, if an array holds n=5 drives of 250GB size, and efficiency is n-1, then available space is 4 × 250GB, or roughly 1TB.
so the more hard drives you have, the less capacity you have according to 1/n ? Can that be right? Even the "unit" is not correct... (n-1) is still in TB... 1/n is like 1 / TB. What is that? Shouldn't it be something like n / 2?
The screenshot is here: