Also note that the new option to create tiered storage is grayed out. This is because the devices in the pool currently don't meet the minimum requirements due to the Unknown MediaType of my physical disk storage.
Enclosure awareness provides fault-tolerance for an entire enclosure failure, by ensuring that data copies are spread across the available enclosures, such that the loss of an entire enclosure still allows access to the data.
Storage Spaces is a technology in Windows and Windows Server that can help protect your data from drive failures. It is conceptually similar to RAID, implemented in software.
Storage Spaces cannot be used to directly host the Windows startup disk or page file (though virtual hard disks can be safely stored in a storage space).
This worked fine and the final pool had a capacity of 43.7TB
if it is software, check everything, drivers, configuration, windows compatibility, the lot. windows is very finicky about this and something small can set something like this off
if you are still having the problem then it may lie someone else, for example the HBA controller on a third party HBA card or the SATA controller on the MB itself.
Check the disks have the correct Media Type after being added to the pool, it's common for them to be listed as Unknown. You can only check this and change the Media Type after you add disks to a pool.
To really get to the bottom of the issue a premier support ticket would have to be logged with Microsoft but that costs money or uses allocated support time from your support agreement so it's not something I would do as we don't use Storage Spaces at work for any real production usage, plus I don't have the issue so I'd first have to find a way to re-create it.