User manual APPLE XSAN 1.4 ADMINISTRATOR GUIDE

[. . . ] Xsan Administrator's Guide for Xsan 1. 4 K Apple Computer, Inc. © 2006 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. [. . . ] You can change some storage pool settings on an existing SAN, but other changes require the associated volume to be reinitialized. Edit button To view or change storage pool 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 about changing specific storage pool settings. 90 Chapter 3 Managing SAN Storage Renaming a Storage Pool You can rename a storage pool, but doing so erases all data on the storage pool and the volume it belongs to. Warning: When you rename a storage pool, all data on the storage pool and the volume to which it belongs is lost. To rename a storage pool: 1 Unmount the associated volume from all clients. In Xsan Admin, select the volume, click Clients, select clients in the list, and click Unmount. Select the SAN, click Setup, click Storage, and double-click the storage pool in the list. From the Command Line You can also rename a storage pool by modifying the associated volume configuration file in Terminal. For more information, see the cvfs_config man page or "The Configuration Files" on page 181. Chapter 3 Managing SAN Storage 91 Choosing the Types of Files Stored on a Storage Pool You can limit the files that are stored on a particular storage pool to volume journal data and metadata, user data, user data with an affinity for that storage pool, or a combination of these. Warning: When you change the data type of a storage pool, all data on the storage pool and the volume to which it belongs is lost. Journal data and metadata are always stored on the first storage pool in a volume. To choose the data types for a storage pool: 1 In Xsan Admin, select the SAN the storage pool belongs to, click Setup, and click Storage. 3 Next to "Use for, " choose the data types to store on the storage pool. 4 Click OK, and then click Save. Setting Storage Pool Stripe Breadth The default stripe breadth value (256 file system blocks) is adequate for storage pools in most SAN volumes. However, you can adjust this value along with the file system block allocation size to tune SAN performance for special applications. For help choosing a stripe breadth, see "Choosing Stripe Breadth for a Storage Pool, " below. Warning: When you change a storage pool's stripe breadth, all data on the storage pool and the volume to which it belongs is lost. 92 Chapter 3 Managing SAN Storage To set the stripe breadth: 1 In Xsan Admin, select the SAN that the storage pool belongs to, click Setup, and click Storage. 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: 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) Chapter 3 Managing SAN Storage 93 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. [. . . ] In Xsan, metadata is managed by a metadata controller and exchanged over an Ethernet connection, while actual file data is transferred over a Fibre Channel connection. metadata controller The computer that manages metadata in an Xsan storage area network. mount (verb) In general, to make a remote directory or volume available for access on a local system. In Xsan, to cause an Xsan volume to appear on a client's desktop, just like a local disk. [. . . ]