User manual APPLE XSAN 2 ADMINISTRATORS GUIDE

[. . . ] Administrator's Guide Xsan 2 K Apple 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 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. [. . . ] To change a folder affinity: 1 In Xsan Admin, select File Management in the SAN Assets list. 2 Select the folder, choose Set Affinity from the Action (gear) pop-up menu, and then choose the new affinity tag. Files already in the folder are not automatically moved to the new storage pool. To move the files that were in the folder to a storage pool with the new affinity tag, use the snfsdefrag command in Terminal. For information and an example, see the snfsdefrag man page. Removing an Affinity You can undo a folder's affinity for a storage pool by choosing None for the folder affinity. To remove the affinity tag from a folder: 1 In Xsan Admin, select File Management in the SAN Assets list. 2 Select the folder, choose Set Affinity from the Action (gear) pop-up menu, and choose None for the affinity tag. 60 Chapter 4 Managing SAN Storage Changing Advanced Volume Settings If your SAN volume has special configuration requirements, you can change the standard volume settings when you create a volume. You can also change these settings for an existing volume, with the exception of the volume name and block allocation size. Note: To change a volume's name or block allocation size, you must destroy and recreate the volume. To view or change volume settings: m Select Volume in the SAN Assets list, select the volume in the list, and choose Edit Volume Settings from the Action (gear) pop-up menu. The following sections contain information about each setting. Chapter 4 Managing SAN Storage 61 Setting the Block Allocation Size Xsan uses the volume block allocation size together with the storage pool stripe breadth to decide how to write data to a volume. If you create a volume based on a built-in volume type (for example, General File Server or Calendar Server Cluster), Xsan Admin sets optimal values for you. For most volumes, the preset block allocation size and storage pool stripe breadth result in good performance. However, in some cases you might be able to improve read or write performance by adjusting these settings to suit a specific application. For example, if your application reads and writes small blocks of data, you might improve performance by choosing a correspondingly small block allocation size. For example, if your application reads and writes 16 KB blocks of data, you can try adjusting the block allocation size to 16 KB and then calculate a corresponding stripe breadth for the volume's storage pools using this formula: stripe breadth = (transfer size / number of LUNs) / block allocation size where stripe breadth is expressed in blocks, and transfer size and block allocation size are expressed in bytes. Computers running Mac OS X or Mac OS X Server have an optimal transfer size of 1 MB. If in the example there are four LUNs in the volume's data storage pools, the calculation for becomes: stripe breadth = (1048576 / 4) / 16384 This gives a stripe breadth of 16. 62 Chapter 4 Managing SAN Storage Changing the Volume Allocation Strategy You can change the allocation strategy for a volume to choose how storage for new files or additional storage for existing files is allocated on the storage pools that belong to the volume. Â Round Robin: Each new request for space is assigned to the next available storage pool in the volume. Â Fill: All data is stored on the first storage pool until it is full, then on the next storage pool, and so on. Â Balance: New data is written to the storage pool that has the most free space. Enabling or Disabling Spotlight on a Volume You can use Xsan Admin to control whether a volume is indexed and searchable using Spotlight. To enable or disable Spotlight on a volume: 1 In Xsan Admin, select Volumes in the SAN Assets list. 2 Select the volume and choose Edit Volume Settings from the Action (gear) pop-up menu. [. . . ] RAID level A storage allocation scheme used for storing data on a RAID array. Specified by a number, as in RAID 3 or RAID 0+1. 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. [. . . ]