Xsan 2.2: Enabling native extended attributes

If all of the computers on your SAN are running Xsan 2.2 or later, you can enable native extended attributes on your SAN volumes to improve volume performance and efficiency.

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Important: Once enabled, native extended attributes cannot be disabled on the volume.

To enable native extended attributes:

  1. Open Xsan Admin.
  2. Select Volumes in the SAN Assets list.
  3. Select the volume to enable native extended attributes on.
  4. Choose "Edit Volume Settings" from the Action (gear) menu.
  5. Select “Enable on this volume” next to Extended Attributes.

The time it takes to convert the volume to use native extended attributes depends on the number of files on the volume, and might be several hours for a large volume. During this time, the volume is mounted on the converting controller only. The volume is mounted on clients and other controllers when the conversion is finished.

When you enable native extended attributes, a tool called dotclean is run, which converts ._AppleDouble files into natively-stored extended attributes.

Troubleshooting extended attribute creation

In some cases, Xsan Admin may become unresponsive while enabling native extended attributes. As noted above, this conversion process may take several hours, but if the progress bar remains fixed at "Converting extended attributes..." for a long time, you can use the following command to see if the conversion process is still running.

ps -ax | grep dotclean

If it is, wait for the process to complete. If not, you can force quit Xsan Admin to recover.

In some cases, Xsan Admin may report that a volume did not start on one or more metadata controllers after enabling native extended attributes. If this happens, manually stop and restart the volume.

In some cases, Xsan Admin may report "An error with the runDotClean command." If this occurs, you must run the dotclean tool manually to complete the conversion.

  1. Start the volume, if it is stopped.
  2. Mount the volume on the hosting metadata controller
  3. Execute the following command in Terminal:
    /usr/share/servermgrd/bundles/servermgr_xsan.bundle/Contents/Resources/dotclean_wrapper.sh /Volumes/VolumeName

    Where VolumeName is the name of the volume.

 

You can verify that all ._AppleDouble files have been converted by running the following command:

sudo ls -1aRl /Volumes/VolumeName | grep "\._" | wc -l

If the output is "0" the AppleDouble files have been converted. This command may take a long time to complete.

 

  1. When the process completes, mount the volume on remaining SAN computers.

The dotclean process may not complete if there is very limited free space available on the volume. In this case you will see the message "unlink: No space left on device" in the file /var/run/dotclean_output_VolumeName.txt. Delete files to create more free space, then run the command manually as described above.

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