tomorrowsman

Thank you everyone for your help; I will start a new thread with I think a much simpler question!

At the absolute most raw level, couldn't I add the SSD to the array, rebuild parity, then remove the HDD and rebuild parity again, with no data loss? I know that is a super ham-handed way to approach the problem, but wouldn't it work, given none of the drives are greater than half the size of my parity drive? I'm asking about alternatives because I do not see any "Copy" function in any of the menus that would enable me to copy the HDD to the SSD, so I'm guessing it's something above my very low level of expertise.

So I remove the HDD from the array, add the SSD to the array, mount the HDD as a UD, then copy to the SSD?

Apologies, I do not know what that means. Did I refer to that in one of my steps?

Yikes, that sounds scary...so I'm not missing anything, is it: Shut down array. Remove HDD, add SSD, reboot array. Add SSD to array via New Config tool. Rebuild Parity - I'm not technical so forgive me, but why wouldn't parity write to the new SSD at this time? I think this is the part of how parity works that confuses me the most; can't the array see the SSD as a new drive replacing a dead drive and use parity plus the other drives to rebuild? Or is this where the start sector issue becomes the issue? Format the SSD - I assume in the dashboard? Mount HDD to the array via Unassigned Devices - though if I'm already at my max SATAs I'm blocked here... Copy data back, meaning, rebuild the array again? Shut down, remove HDD, reboot?

I've been using unRaid since 2012 and have swapped out countless drives over that time. My 4TB WD HDD hard drive is on the way out, so I decided to replace it with a new Crucial MX500 SSD, others of which I've had in my array for years. For some reason I'm getting an error that "the disc must be as big or bigger than the original" even though both are 4TB. Is there any way to have my unRaid OS work through this? In all these years and swaps I've never encountered this before.