Choose an allocation strategy for an Xsan volume

Learn how to modify the allocation strategy for Xsan volumes on computers running OS X Yosemite or later.

 Your strategy determines how the system allocates space on the storage pools that belong to the volume. Xsan volumes support these three allocation strategies:

  • round: Each request for space is assigned, in turn, to the next available storage pool in the volume. This is the default allocation strategy for Xsan volumes.
  •  fill: All data is stored on the first storage pool until it's full. Data is then stored on the next storage pool, and so on.
  • balance: New data is stored on the storage pool that has the most free space.

Follow these steps to change the allocation strategy for your Xsan volume. In each command, replace VolumeName with the name of your Xsan volume.

  1. On your primary metadata controller, make two copies of the volume configuration file and save them to your desktop:
    cd /Library/Preferences/Xsan
    cp VolumeName.cfgp ~/Desktop/VolumeName.cfgp.original
    cp VolumeName.cfgp ~/Desktop/VolumeName.cfgp.modified
  2. In the second copy of the volume configuration file (VolumeName.cfgp.modified), set allocationStrategy to round, fill, or balance. For example, to set the strategy to round:
    /usr/libexec/PlistBuddy -c 'delete :config:globals:allocationStrategy' -c 'add :config:globals:allocationStrategy string round' ~/Desktop/VolumeName.cfgp.modified
    Note that this value is case-sensitive. You'll see an error if you use “Round” instead of “round.”
  3. Check the modified copy of the volume configuration file:
    sncfgvalidate -n VolumeName -f ~/Desktop/VolumeName.cfgp.modified
  4.  In the output, look for "VolumeName validated." If you see an error instead, you must fix it before you can continue to step 5. Alternatively, you can quit the procedure here since you’ve changed only the copy of the configuration file.
  5. Replace the original configuration file with the modified copy:
    sudo cp ~/Desktop/VolumeName.cfgp.modified /Library/Preferences/Xsan/VolumeName.cfgp
  6. Update the Xsan configuration that's stored in LDAP:
    sudo xsanctl pushConfigUpdate
  7. Restart the Xsan volume:
    sudo cvadmin -e 'stop VolumeName'
    sudo cvadmin -e 'start VolumeName'
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