Allow to install the Operations Manager DB in a SQL cluster instance with mount point
1. Installing a SQL cluster with mount points is supported https://support.microsoft.com/en-us/kb/819546
2. Operations Manager supports hosting the DB in a Failover Cluster configuration https://technet.microsoft.com/en-us/library/dn249696.aspx
You can use SQL Server failover clustering or SQL Server 2012 AlwaysOn
3. Mount Point configuration is considered a Failover Configuration Instance FCI
4. The installation of the Operations Manager database cannot be completed because it is unable to detect disk space available where the data files are located in the SQL instance FCI with mount points https://support.microsoft.com/en-us/kb/2702933
System Center 2012 Operations Manager setup cannot determine the free disk space for the operational database if the target directory for the Data file folder or the Log file folder is within a mounted NTFS folder and the free disk space of the volume the folder is mounted to is less than 1024 MB for the Data file and less than 50% of the database size for the Log file. This occurs despite the fact that there is enough free disk space on the volume hosting the mounted folder.
5. Same behavior is experienced when using Cluster Shared Volume CSV, the DB installation cannot be completed.
6. There is no documentation provided by PG where mentions using SQL FCI with mount points is supported