Windows 2012 Storage Spaces not mounting after reinstall

After reinstalling Windows 2012 R2 Server you may find that the Storage Spaces virtual disks will not show up automatically. In fact you won’t even see them in “Computer Management”.

The reason for this is that the server is not configured to use the old storage space setup.

Authorize server for read-write to storage spaces

First you must authorize the server to write to the storage spaces. There are two ways to do this:

1. From GUI: Server Manager->File and Storage Services->Volumes->Storage Pools.
   1. Right-click your storage pool and choose “Set Read-Write access…”
      
   2. Choose your server and click OK.
      
2. From PowerShell:
   1. Get a list of storage pools available:
      Get-StoragePool
   2. Change the storage pool you want to read-write:
      Set-StoragePool -FriendlyName YourStoragePool -IsReadOnly $False
   3. Check the result:
      Get-StoragePool

Second you must attach the disks. You can do this from GUI, but it will not be persistent across reboots. Under “Storage Pools” simply right-click the disk you want in “Virtual Disks” window and select “Attach”. To make disks automatically mount / attach during boot you will need to use PowerShell:

1. Get a list of virtual disks:
   Get-VirtualDisk
2. Change IsManualAttach to $False. In this command I assume you want to change all in one go:
   Get-VirtualDisk | Set-VirtualDisk -IsManualAttach $False
3. Check the result:
   Get-VirtualDisk

Reboot to see the result in its full glory.

If the disks have not been assigned drive letters in Windows simply go to “Computer Management” (under Administrative Tools in Control Panel), select “Storage->Disk Management”, right click the disk and select “Online”, “Change Drive Letter or Path” or whatever is needed to finalize the mount job.

Summary

Windows 2012 R2 Server will not automatically mount any storage space it sees. You must tell it how to treat the storage space. Changing the IsReadOnly flag can be done from GUI, but changing the “IsManualAttach” flag can’t.

So if you want your storage pool virtual disks to act as one would expect a RAID disk in a server to do then “Set-VirtualDisk -IsManualAttach $False” is the way to go.