Apple Xsan 2 - Manual (Page 80)

View or change volume settings:
Select Volume in the SAN Assets list, select the volume in the list, and choose Edit
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Volume Settings from the Action pop-up menu (gear).
The following sections contain information about each setting.
Set the block allocation size
Xsan uses the volume block allocation size with the storage pool stripe breadth to
decide how to write data to a volume. If you create a volume based on a built-in
volume type (for example, General File Server or Podcast Producer Cluster), Xsan
Admin sets optimal values for you.
For most volumes, the preset block allocation size and storage pool stripe breadth
result in good performance. However, in some cases you might be able to improve
read or write performance by adjusting these settings to suit a specific app. For
example, if your app reads and writes small blocks of data, you might improve
performance by choosing a correspondingly small block allocation size.
Set a volume’s block allocation size:
The block allocation size must be set when the volume is created, and can’t be
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changed for an existing volume. To set the block allocation size, click the Advanced
Settings button on the Volume Name and Type pane when you first add the volume.
Change the volume allocation strategy
You can change the allocation strategy for a volume, to choose how storage for new
files or additional storage for existing files is allocated on the storage pools that
belong to the volume.
Change the allocation strategy:
1 In Xsan Admin, select Volumes in the SAN Assets list.
2 Select the volume in the list and choose Edit Volume Settings from the Action pop-up
menu (gear).
3 Choose an allocation strategy from the pop-up menu:
Round Robin: Each request for space is assigned to the next available storage pool in
the volume.
Fill: All data is stored on the first storage pool until it’s 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.
Note: After you click OK, the volume restarts.
80 Chapter 5 Manage SAN storage