SQL server, Analysis Services and mount points

You will find below a summary of important points to know to use the mount points with SQL Server.

SQL Server and SSAS supports mount points in cluster if and only if at least one letter named as the primary drive by instance. Then you can add your mount points.

You must also meet the following prerequisites:
1. You can not put the files directly to the root mount point. It is imperative to create the root of each mount point, a directory, then place the files in that directory.
2. As part of a cluster for each mount point, you must create a cluster resource. Then add a dependency to indicate that SQL Server will not start if all dependencies and disk mounting points are not all online.

In addition, references to KB articles:

1. FIX: You are prompted to format the volume when a formatted volume is mounted on a NTFS folder that is located on a computer that is running Windows Server 2008 or Windows Vista (https://support.microsoft.com/kb/971254/ )

2. It is recommended not to put files to the root of the mount point for support by Microsoft for support. Solution: create a directory to deposit your files.

E.G. SQL Server 2008 setup fails to install on a Windows Server 2008-based cluster mount point(https://support.microsoft.com/kb/2216461/)
“Note: SQL Server does not support installing to the root of the Volume Mount point because the permissions are not propagated to the Mount Point since Windows does not let you replace permissions on the root of a volume. To prevent problems during new installations and applications of updates to SQL Server, to create a folder on the root of the mount point and install to that folder. At this point, permissions are set correctly. If you previously installed to a root directory, we highly recommended that you create a folder, validate the current database integrity by using the DBCC CHECKB process, and then move the database to the folder.” To work around this problem, simply create the root of each mount point, directory, then move the files in that directory.

3. Cluster : Dependencies and mounts point : https://support.microsoft.com/kb/819546/
“The SQL Server 2005 (and later versions) resource depends on the SQL network name resource and the physical disk resources that hold its data. When mount points are being used together with the physical disks, each mount point must appear as a cluster resource. Additionally, each mount point must also be added as a SQL Server dependency. If only the root physical disks dependency is added and the mount points are not added, database corruption will occur on failover. Database corruption may also occur when SQL Server is restarted without failing over.”

4. Cluster : SQL Server support for mounted volumes(SQL 2000,2005 and 2008) : 
"Because of the number of available drive letters, the number of the virtual instances on a cluster is limited to 25. SQL Server 2005 and later versions have the same limitation. SQL Server supports use of mount points hosted only by drives that have drive letters that are not hosted by other mount points."  (https://support.microsoft.com/kb/819546)

Michel Degremont | Premier Field Engineer - SQL Server Core Engineer |