If you want to check the any disks available to add in the storage pool for servers, you can use the below command.
Get-PhysicalDisk -CanPool $True
Below is the information regarding the storage pool.
The storage pool is a set of disks on which the Data Protection Manager (DPM) server stores replicas, shadow copies, and transfer logs. Before you can start protecting data, you must add at least one disk to the storage pool. Disks added to the storage pool should be empty.