Different size drives on a mirror RAID 1 set

I have a failed drive 1. Can I replace it with a larger size drive than the original 2TB and remirror?

Hi warrenw,

Since your drive was configured in RAID 1 so you have to use the same size drive in RAID 1. So, you cannot use the larger size drive in RAID 1.

I have the very same situation. Please forgive my ignorance and clarify your answer. I should be able to replace one of the drives with a new same-sized drive right? How is replacing it with a larger sized drive any different?
Would it be possible to remove all my data and then reconfigure the entire MyCloud Mirror over again in RAID 1 with two different sized drives?

RAID 1 is mirroring, so the content of one drive is automatically also written to the second drive.

A moment’s thought should tell you that this will only work with equally sized drives, or else at some point the smaller one would be filled before the larger one is, and then you can’t have parity between the drives any more.

The best you could do is partition the larger drive down to being the same size as the smaller one so they both appear to be the same size, but that’s not exactly an efficient usage of the larger drive.

Thanks. Partitioning the larger drive is of interest.

I’m counting in the original drives failing at some point. It has been about 3 years since I purchased them. Replacing one now with a new drive hopefully starts the clock again. Unfortunately I am also filling up the original space that I started with so I also need to grow capacity over time. I don’t mind if I don’t use the remaining portion for a few more years until I ready to replace the second one. This keeps the date of my drives staggered and hopefully reduces the chance that they both fail at about the same time — a catastrophic event I want to avoid at all costs.

I’m sure there is a better way of doing this, if so, please let me know.


It’s an inherent restriction of RAID 1, which some of the other RAID versions using more than 2 disks don’t suffer from. In such a case and for mission critical data you’re probably better using two devices in two distinct locations anyway, at which point the whole question is moot.

I’m actually in a similar situation myself - my MCM rev.1 is older than yours, and is quite full (as are the 2x 5TB elements drives on its USB ports). I’m looking at changing over to something with a higher capacity, but it will almost certainly be a whole new device with multiple bays (certainly more than 2) to allow use of RAID 5 or something similar.

you can replace with a same drive size or a larger drive size. But NOT replace with a smaller drive size. If replace with a larger drive size. It will only use the same space amount as the other drive size.