Installing SQL Server SP1 on SQL 2012 Failover Cluster Instance (FCI) failed with  the following error:

There was a failure to calculate the default value of setting PatchResult.

Error code 0x85640001

The issue was that when you launch SQLServer2012SP1-KB2674319-x64-ENU.exe, it creates a temporary folder (something like g:\27eb5c29eceb5ae55b8b531263faacc) with setup files on a cluster disk which happened to store SQL data files.

During SP1 installation, it restarts the SQL Server service which then took the cluster disk where SQL data files and the SP1 temp folder hosted offline, then the service pack was trying to read from disk that is unavailable caused the install to fail.

The workaround is to copy the SP1 temp folder to the local c:\ drive and run Setup from c:\ location, SP1 installation completed with no problems.

I know it sounds weird but the SP1 will extract the files to whatever drive has more space and in this case was a cluster disk.