Apple Xsan 1.4 - Manual (Page 46)

46 Chapter 2 Setting Up a Storage Area Network
For a more typical balance of security and shared access, a flexible compromise is to
create a single volume and use folder access privileges or access control lists in
Mac OS X Server’s Workgroup Manager to control access.
Deciding How to Organize a Volume
You can help users organize data on a volume or restrict users to specific areas of the
volume by creating predefined folders. You can control access to these folders by
assigning access permissions using Xsan Admin.
You can assign folders to specific storage pools using affinities. You can, for example,
create a folder for data that requires fast access and assign that folder to your fastest
storage pool.
Assigning LUNs to Storage Pools
You should set up a storage pool using LUNs that have similar capacity and
performance characteristics.
To provide high performance, Xsan uses the RAID 0 scheme to stripe data across the
LUNs in a storage pool. This requires that the LUNs in the pool be the same size. If you
set up a storage pool using LUNs of different sizes, Xsan uses available space on each
LUN equal to the capacity of the smallest LUN. If the LUNs vary in size, this can result in
wasted capacity. For example, if you assign 240 GB and 360 GB RAID arrays to a storage
pool, 120 GB of the larger array will not be used. By combining LUNs with similar
capacities, you avoid wasting available storage.
If you want to set up a storage pool for use by a high performance application, assign
similarly high speed LUNs. Assign slower LUNs to a storage pool where you keep data
that doesn’t have critical performance requirements.