After some quick troubleshooting, I found that the SAN policy for the Virtual Disk Manager is set to “Offline Shared” by default. The SAN policy controls how SAN LUNs are mounted on a Windows Server. This can be confirmed using DiskPart.
Open a cmd prompt as admin and type in “diskpart”. Then type in “san”. This will show you the current SAN policy.
To resolve this, you need to change the SAN Policy to “Online All”. This can be done with a simple command. Back in the diskpart window, type in “san policy=onlineall” :
Now, go back to disk management (or you can just use diskpart) and bring the volume online, then initialize it.