you understand wrong, the disk you pass must be at least as big as the old one for a direct replacement. else, if you have the option to put in all disks you could also create a new pool and zfs send/recv your datasets over. but that requires a...
I have my install on a 2 136g spinning HDDs. I'd like to replace both of them with 120G ssds.
When I use zfs replace rpool current-disk new-disk I get "cannot replace, device is too small.
As I understand it, ZFS should accept a smaller disk...