Apple Xsan 2 (Third Edition) - Manual (Page 18)

Volumes
Storage pools are combined to create the volumes that users see. From the user’s
perspective, the SAN volume looks and behaves like a large local disk, except that:
The size of the volume can grow as you add underlying arrays or new storage pools Â
Multiple users on the SAN can access files on the volume at the same time Â
In the illustration on page 16, five storage pools are combined to create a single shared
volume. You use Xsan Admin to create volumes and mount them on client computers.
The following screen shot shows how LUNs, storage pools, and volumes look as
you organize them in Xsan Admin. This example shows a SAN with a single shared
volume named “SanVol.” Storage for the volume is provided by two storage pools,
“MetadataAndJournal” and “Data1,” the first based on a single LUN and the other on
two LUNs.
Volume
Storage pool
LUN
Folders with Affinities
To control which storage pools are used to store specific files (for example, to provide
different levels of service for different users or applications), you can associate a folder
on an Xsan volume with an affinity tag that’s assigned to storage pools that make up
the volume.
For example, you can associate some folders with an affinity whose storage pools have
faster LUNs, and associate other folders with an affinity whose storage pools have
safer LUNs. Users can choose between faster and safer storage by putting files in the
appropriate folder.
18 Chapter 1 Overview of Xsan