Hello, NINA.
There are some restrictions for expand a disk domain:
Disks at the same storage layer in a disk domain are of the same capacity and have the same rotation speed.
All the disks of one disk domain come from the same engine.
A maximum of 100 member disks can be configured for each layer in a disk domain.
If two or more types of disks are to be added (that is, two or more storage tiers are included),
you are advised to expand the capacity layer by layer. Do not expand the capacity of both storage tiers at the same time.
Hope this can help you!