Apple Xsan 1.1 - Manual (Page 52)

52 Chapter 3 Managing SAN Storage
Adding Storage
There are several ways you can add storage to a SAN:
 Add RAID arrays (LUNs) to existing storage pools
 Add storage pools to existing volumes
 Add new volumes
The first option, adding LUNs to a storage pool, increases available storage and can
improve the performance of the SAN because it increases the number of RAID
controllers and data paths between clients and storage. You’ll need to stop the volume
and unmount it from clients before you add LUNs to any of its storage pools.
Note: You can’t add LUNs to an existing storage pool that is being used to store journal
data or metadata.
The second option, adding a storage pool to a volume, also increases available storage,
and also requires you to stop the volume and unmount it from clients.
The third option creates a new volume that must be explicitly mounted on client
computers. Clients must then choose to save new files and folders on the new volume,
or copy existing items there, so this option is more likely to disrupt user workflow.
Restoring the Previous Volume Configuration After Changes
If you have trouble with a volume after expanding it, you can restore its previous
configuration so it can be used until you solve the problem. See “You’re Unable to
Restart a Volume After Adding LUNs or Storage Pools” on page 101.
About Rearranging Fibre Channel Connections
If, while expanding or reconfiguring your SAN, you break a Fibre Channel connection
between an Xsan client and a mounted volume for more than one minute, the volume
is unmounted from the client in a way that can cause problems with applications
running on the client and make the volume difficult to remount. To avoid this,
unmount the volume before you disconnect the client.
Important: If a planned change to your SAN requires you to disconnect a Fibre Channel
cable for more than a minute, you should first unmount all Xsan volumes from all
controllers and clients on the SAN, and then either shut down all computers connected
to the SAN or disconnect all of their Fibre Channel cables.