Apple Xsan 1.4 - Manual (Page 93)

Chapter 3 Managing SAN Storage 93
To set the stripe breadth:
1 In Xsan Admin, select the SAN that the storage pool belongs to, click Setup, and click
Storage.
2 Double-click the storage pool in the list.
3 Next to Stripe Breadth, type the new value.
4 Click OK, and then click Save.
Choosing Stripe Breadth for a Storage Pool
Xsan uses the storage pool stripe breadth and volume block allocation size together to
decide how to write data to a volume. For most SANs, the default values for storage
pool stripe breadth and volume block allocation size result in good performance.
However, in some cases you might be able to improve read and write performance by
adjusting these values to suit a specific application.
The stripe breadth of a storage pool is the number of file allocation blocks that are
written to a LUN in the pool before moving to the next LUN. To choose an efficient
stripe breadth, you need to consider two other factors:
 The most efficient data transfer size of the LUN storage device (1 MB for the
combination of Mac OS X or Mac OS X Server and Xserve RAID systems)
 The size of the data blocks written and read by the critical application that uses the
volume (as reflected in the block allocation size for the volume)
Knowing these values, choose a stripe breadth using this formula:
stripe breadth (in blocks) = transfer size (in bytes) / block allocation size (in bytes)