Troubleshooting: In Hyper-V guest environment writeable disk is shown as Read-only
In the Hyper-V guest environment, if a disk is writable but the disk manager or any other Windows utility shows that the disk is in the Read-only state, you need to restart the Hyper-V guest machine.
This can occur during the Migrate or Take over operation. Restarting the guest machine is a one-time activity that is required when you mask the LUNs on the target data center for the first time to a Hyper-V server. Also the LUNs should be Writeable at that time.
This issue is observed when 3rd party replication technology is used.