Before trying it out - I don't find any documentation.
Given that Storage Pools have serious performance problems with parity, and do not rebalance data at the moment when you add discs, my preferred way to use them would be as think provisioned space, ISCSI targets - with every "Pool" running against 1 RAID that comes from a Raid controller (who also introduces SSD read and write caching - another thing missing from Storage Pools).
The main question is - how does a Storage Pool handle the change in the underlying disc that can happen? I mostly talk about OCE (Online Capacity Expansion), where a disc after an expansion suddenly reports a larger space.
Standard Windows allows you to use this additional space (and expand the partitions). How does a storage pool handle it?
For me in testing, expanding the physical underlying disk yielded odd results. get-physicaldisk in PowerShell and the Server Manager Storage Spaces did not show the disk being larger after reboot. In the legacy Disk Management or using get-disk in PowerShell DID show the additional space on disk, but I see no way to add it to an existing Storage Pool.
I tried to find a storage Cmdlet to resize/grow/expand/extend a Storage Pool but didn't see one.
You can't add it to a new Pool because Pool's are disk-based and the physical disk is already in a Pool. Since that Pool disk was being used for a Virtual Disk I could not remove it to try and re-add it.
So either I'm doing it wrong, or Windows Server 2012 Storage Pools can not deal with underlying physical disks expanding.
Note in my testing, what I did was shutdown a 2012 VM and expand a 2nd .vhd file, which would be the virtual equivalent of expanding a physical RAID set on a server.