Not able to install MSSQL 2014 on an additional disk(some disk other than the OSdisk) silently on Windows 2012 R2 I am providing the following paths during installation(and yes, there's no overriding anywhere)-

InstallSQLDataDir = "R:\Microsoft SQL Server\Instance"
SQLBackupDir = "R:\BACKUP\Microsoft SQL Server\Instance\MSSQL12\MSSQL\Backup"
SQLUserDbDir = "F:\DATA\Microsoft SQL Server\Instance\MSSQL12\MSSQL\SQLData"
SQLUserDbLogDir = "L:\LOGS\Microsoft SQL Server\Instance\MSSQL12\MSSQL\SQLLog"
SQLTempDbDir = "T:\\"
SQLTempDbLogDir = "T:\\"
InstallShareDir = "E:\Program Files\Microsoft SQL Server"
InstallShareWowDir = "E:\Program Files (x86)\Microsoft SQL Server"
InstanceDir = "E:\Program Files\Microsoft SQL Server"


Still, everytime, the MSSQL installation happens onto the OSdisk/System Drive/C drive. Why ?
Still, everytime, the MSSQL installation happens onto the OSdisk/System Drive/C drive. Why


What you are seeing is called binaries of SQL Server and as per rule binaries always goes on system drive and you have no control over it.

If you read SQL Server file location of default and named instance you can get various default locations.