Question

What is the difference of the sys.master_files and sys.database_files? I have about 20 databases in my instance but when I query the sys.master_files I do not receive any rows. Why? When I query sys.database_files I get the information about the database files concerning the current database.

Answer 1

sys.master_files :

Contains a row per file of a database
as stored in the master database. This
is a single, system-wide view.

sys.database_files :

Contains a row per file of a database as stored in the database itself. This is a per-database view.

So, SELECT * FROM sys.master_files should list the files for each database in the instance whereas SELECT * FROM sys.database_files should list the files for the specific database context.

Testing this here (SQL 2K8), it works as per the above?

Update:
If you’re not seeing rows from sys.master_files, it could be a permissions issue as BOL states:

The minimum permissions that are
required to see the corresponding row
are CREATE DATABASE, ALTER ANY
DATABASE, or VIEW ANY DEFINITION.

Whereas for sys.database_files just requires membership in the public role.