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SMB Shortnames When a Long-name Already Exists

This article applies to: Shared File Services

In order to maintain compatibility with older forms of PC operating systems, the SMB (or CIFS) protocol includes shortnames. These are often referenced as a “DOS name” or “eight dot three name”. The 8.3 is the character format of a shortname with 8 ASCII characters followed by a period and then 3 characters (representing the filename extension).

This becomes a problem when we need to recover or migrate data where long and short names coexist. If, in the process of a restore or a robocopy, the long-name is written to a destination first, the shortname will be in conflict with it and will produce an error. For example, if you have a file named “AbCdEfGh-0111.txt” written first, when trying to copy the corresponding 8.3 name “ABCDEF~1.TXT“ to the same folder, an error will occur.

For this reason, SFS cannot guarantee recovery of data if long and short named files co-exist in the same folder. There are ways around this.

  • The first one is to clean up the data. If the long-name and shortname files have identical content and both are in the same folder, remove the shortname file.
  • The second is to robocopy the files by first sending the 8.3 names followed by long-name files.
  • Another option is to add replication to your share.

For technical details, refer to the Microsoft SMB specifications.


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