OS X Mavericks: About extended attribute size on AFP and SMB servers

In OS X Mavericks, the maximum supported extended attribute size is 2 GB. This is greater than what was supported in earlier OS X versions.

The maximum supported extended attribute size for all AFP servers and SMB servers prior to Mavericks is 128 KB. If an AFP server has extended attributes whose size is greater than 128 KB or if a Mavericks client is connected to a pre-Mavericks server, the following may occur:

  • Applications may have issues when reading extended attributes that have a size greater than 128 KB via getxattr(2). The application can still read extended attributes up to 128 KB size without issue.
    Note: listxattr(2) and removexattr(2) work as expected.
  • If a file is copied in Terminal via the cp command, extended attributes larger than 128 KB will not be copied.
  • If a file with any extended attribute is copied via the Finder, no extended attributes will be copied.

Note: There shouldn't be any issues with listing extended attribute names and their sizes via the Terminal command ls -l@. Also, Mavericks SMB servers and third-party servers that support named streams should not be affected.