Follow up the following steps:
1. Configure your SAN to present your disks to the Cluster Servers.
2. Detect the new disk’s at Windows Storage Manager (on both servers):
3. Add this new this to the cluster Service (Go to Server Manager –> Features –> Failover Cluster Manager –> Storage –> Right Click and click Add a Disk):
4. Go to Failover Cluster Manager –> Services and Applications, and right click SQL Server and then select “Add storage”:
5. Now it’s important, after the step 4 you can see the disk at cluster service associated to the SQL Server Service, but at SQL Server Manager, you can’t see the disk! So, you just need to add service dependence:
Right Click SQL Server Resource, and click Properties:
Click on Dependencies Tab, and then click on the last line to add a new line, and select “AND” and then select the new disk resource:
Now click Apply and OK and the new disk is now available to the SQL Server Service!