When you back up a database or a database log to a network share Universal Naming Convention (UNC) path in Microsoft SQL Server 2014 or Microsoft SQL Server 2012, the network storage device indicates that SQL Server searches for the filestream.hdr file in its parent directories. This generates some unexpected overhead on certain storage devices.
This issue occurs because SQL Server checks for the filestream.hdr file to prevent a file from being backed up to a FILESTREAM container. However, this is generally unnecessary for a network share.
Cumulative update information
This fix relaxes the check for a UNC path.
The issue was first fixed in the following cumulative update of SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.