Should you disable 8.3 filenames?

An old Microsoft KB article describes how you can disable the creation of 8.3 filenames for NTFS, see

http://support.microsoft.com/kb/210638

Some admins do this because they believe there is filesystem overhead associated with the creation of 8.3 filenames, so for “performance reasons” they disable it on their file servers, especially when the server has a large number of files in a single directory .  But is disabling 8.3 filenames really a good idea?

Probably not.  If you disable 8.3 filenames it can break some of the mitigations to MAX_PATH that are built into the Windows operating system when file system names longer than 260 characters are handled.  Also, Microsoft probably hasn’t tested Windows with 8.3 filenames disabled as it has with 8.3 filenames enabled, so disabling 8.3 filenames can lead you into uncharted territory.

The real problem is how you plan the directory structure of your file server.

Mitch Tulloch is a seven-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.

2 thoughts on “Should you disable 8.3 filenames?”

  1. Have you tested your theory? Microsoft tells you explicitly that it is best practice to turn off 8.3 notation for FILESTREAM support in SQL Server. One of the major reasons is that the GUID based filenames are highly repetitive, so there will be a lot of collisions on that data. I might suggest it is very well tested indeed.

    The payoff to this performance enhancement depends largely on the number of similarly named files you will have in a directory. If your filenames are based off of a GUID or a UUID, then turning off 8.3 notation is a huge win–particularly when you have hundreds of thousands of files in a single directory (i.e. in the FILESTREAM support case).

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