User manual APPLE XSAN 1.1 ADMINISTRATOR GUIDE

[. . . ] Xsan Administrator's Guide Information for setting up and managing Xsan volumes in a storage area network using Xsan Admin or the command line For Xsan 1. 1 K Apple Computer, Inc. © 2005 Apple Computer, Inc. All rights reserved. Under the copyright laws, this manual may not be copied, in whole or in part, without the written consent of Apple. The Apple logo is a trademark of Apple Computer, Inc. , registered in the U. S. Use of the "keyboard" Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of Apple may constitute trademark infringement and unfair competition in violation of federal and state laws. [. . . ] 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: Â 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) Â 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) For Xserve RAID systems, which have an optimal transfer size of 1 MB, this becomes: stripe breadth = 1048576 / block allocation size If, for example, you are using an application such as Final Cut Pro to move large amounts of video data, choose the largest block allocation size (512KB) and use the equation to find the stripe breadth of 2 blocks. Then, Xsan writes 1 MB of data (two 512KB blocks), in turn, to each LUN in your video storage pool. 62 Chapter 3 Managing SAN Storage Setting Storage Pool Access Permissions You can set up storage pools for read-write or read-only access. To set storage pool access permissions: 1 In Xsan Admin, select the SAN the storage pool belongs to, click Setup, and click Storage. 2 Double-click the storage pool in the list. 3 Choose Read & Write or Read Only from the Permissions pop-up menu. From the Command Line You can also set read or write access to a storage pool using the cvadmin enable command in Terminal. For more information, see the cvadmin man page or "Viewing or Changing Volume and Storage Pool Settings (cvadmin)" on page 109. Setting the Selection Method for Multiple Connections If there is more than one Fibre Channel connection to the LUNs in a storage pool, you can choose whether Xsan alternates between connections for each write or statically assigns each LUN in the volume to a connection at volume mount time. This is called the "multipath method. " To change the multipath method: 1 In Xsan Admin, select the SAN the storage pool belongs to, click Setup, and click Storage. 2 Double-click the storage pool in the list. 3 Choose a value from the Multipath Method pop-up menu. Static: Xsan assigns each LUN in a storage pool to one of the connections when the volume is mounted. Rotate: Xsan switches to a different connection each time it writes data to the storage pool. From the Command Line You can also set the multipath method using the cvadmin multipath command in Terminal. For more information, see the cvadmin man page or "Viewing or Changing Volume and Storage Pool Settings (cvadmin)" on page 109. Chapter 3 Managing SAN Storage 63 Changing Volume Settings You can change some settings for an existing volume, but other changes require the volume to be re-initialized (you'll see a warning for these cases). Edit button To view or change volume settings: m Select the SAN in the SAN Components list, click Setup, and click Storage. Then select a storage pool and click the Edit button (or double-click a storage pool). See the following pages for information on changing specific storage pool settings. 64 Chapter 3 Managing SAN Storage Renaming a Volume You must use Xsan Admin to change the name users see when the volume is mounted on their computers. You can't rename Xsan volumes using the Finder. Warning: Renaming a volume causes all data on the volume to be lost. To rename a volume: 1 Unmount the volume from clients. In Xsan Admin, select the volume and click Clients. [. . . ] Can be set to static, which assigns each LUN in a storage pool alternately to one of the connections when the volume is mounted; or rotate, which alternates between the connections for higher performance. RAID array A group of physical disks organized and protected by a RAID scheme and presented by RAID hardware or software as a single logical disk. In Xsan, RAID arrays appear as LUNs, which are combined to form storage pools. 128 Glossary round robin An Xsan storage pool allocation strategy. In a volume consisting of more than one storage pool, Xsan allocates space for successive writes to each available pool in turn. [. . . ]