UPDATE Mar. 10: This issue is now resolved. The fix has been fully deployed to all Windows Azure hosts. There is no action needed within the VM itself, as the fix was on the Windows Azure hosts.
We recently determined the Storage Spaces feature in Windows Server 2012 R2 is not compatible with the virtual hard drives (VHDs) created by Windows Azure for use as data disks for the Virtual Machines feature (IaaS). Not only will the disks not enumerate in Server Manager, but they will also show up as CanPool=False when enumerated using Get-PhysicalDisk in PowerShell. The same VHDs work fine when used with Windows Server 2012. The root cause of the problem is that the physical disk size advertised by Azure VHDs is not compatible with Windows Server 2012 R2 Storage Spaces.