That is not true. I have an Intensio 2TB Model with 3907029168 sectors and a WD 2TB model with 3906963456 sectors. See the following box for proof. Proof that same size hard drives can have different amount of sectors One of my Intensio drives broke down (Disk1). The other one of my Intensio drives (exact same model) is still running as Parity1. So I bought a new 2TB disk, to replace the broken Disk1. Unfortunately that disk has 65712 sectors less than my current intensio dives. But UNRAID will only let you replace a disk with a disk that has an amount of sectors >= the amount of sectors of you current disk. So I think my options are: Buy many more 2TB disk from different manufacturers until I find one that has by chance equal or more sectors than my broken Intensio drive. Whenever I need to replace a disk I upgrade to the next higher tear (2TB -> 4TB -> 6TB -> 8TB -> ...). Eventually I will either run out of money or there won't a bigger disk to buy. I don't like these options as they are both not sustainable. Therefore I want to implement the following strategy: I define a number of sectors as my standard, say 3906000000. Every 2TB hard drive will easily have more than this amount of sectors. Also I don't need the full 2TB, so it does not hurt to shrink the amount of sectors that are available to me. Whenever I want to add a new disk to my array, I will first create a partition on that disk that is exactly 3906000000 sectors in size. This way I will always be able to replace any 2TB disks with any other 2TB disk, because my disk will always have the exact same size, even if manufacturing varies. I just got a little problem with this strategy. I am already operating a 2TB drive that is bigger than my future standard. So I would have to shrink that disk while there is productive data on it. Since I am not an expert, I asked ChatGPT how to do that. But since ChatGPT is known to hallucinate, I ask this community whether the approach that ChatGPT suggested is safe. If you have a better strategy for this problem, that does not involve me dribbling the partitions of a disk that is in productive use, then I would appreciate it if you share it. To summarize: Hard drives of different manufactures do have different amounts of sectors UNRAID will only allow you to replace a disk if it has the same or a greater amount of sectors Because of bad luck, the replacement disk that I bought does not have an equal or greater amount of sectors than my current disk What is the best strategy to deal with that? If the strategy that I explained above actually is the best strategy for this problem: how do I implement the strategy safely, given that my hard drives are already in use? Thanks!