Apple Xsan 1.1 - Manual (Page 67)

Chapter 3 Managing SAN Storage 67
Setting the Volume Allocation Strategy
You can set the allocation strategy for a volume to determine the order in which data is
written to the volume’s storage pools.
To set the allocation strategy:
1 In Xsan Admin, select the SAN the volume belongs to, click Setup, and click Storage.
2 Double-click the volume in the list.
3 Choose a value from the Allocation Strategy pop-up menu.
Round Robin: New data is written to the next available storage pool in the volume.
Fill: All data is stored on the first storage pool until it is full, then on the next storage
pool, and so on.
Balance: New data is written to the storage pool that has the most free space.
4 Click OK, then click Save.
Checking Volume Fragmentation
When you create a file, Xsan breaks the file into pieces and distributes these pieces
efficiently over the LUNs that make up one of the volume’s storage pools. Over time, as
the file is modified, its pieces can become scattered in less efficient arrangements. You
can use the
cvfsck utility to check on the state of file fragmentation on your volumes.
To check volume fragmentation:
1 Open Terminal (in /Applications/Utilities).
2 If you are not working at the SAN controller computer, use SSH to log in to the
controller remotely:
$ ssh user@computer
where
user
is an administrator user on the controller computer and
computer
is the
controller’s name or IP address.
3 Run the
cvfsck
command-line utility (in /Library/Filesystems/Xsan/bin) with the
-f
option:
$ sudo cvfsck -f volume
For more information, see the
cvfsck
man page.
Warning: When you change a volume’s allocation strategy, all data on the volume
and its storage pools is lost.