Apple Xsan 2 - Manual (Page 77)

Chapter 5 Manage SAN storage 77
5 In the Configure Volume Storage pane, drag the new LUNs to affinity tags.
Important: Add LUNs to affinity tags in the recommended multiples. Don’t add
LUNs to existing storage pools in a custom volume. Otherwise, serious volume
fragmentation can result.
6 Click Continue to unmount and stop the volume, add the storage, and remount the
expanded volume.
From the command line
You can also add LUNs to an affinity tag by editing the associated volume
configuration file and using the
cvlabel command-line tool in Terminal. For
information, see the cvfs_config and cvlabel man pages or “Xsan configuration
files” on page 158 and “Label, list, and unlabel LUNs (cvlabel)” on page 151.
You can see the cvfs_config man page by entering this command in Terminal:
$ man -M /System/Library/Filesystems/acfs.fs/Contents/man/ 4 cvfs_config
Rearrange Fibre Channel connections
If you need to rearrange Fibre Channel connections when adding LUNs to your SAN,
unmount SAN volumes from clients before you disconnect Fibre Channel cables or
turn off Fibre Channel switches. Otherwise, if you unplug or interrupt a Fibre Channel
connection between a client and a mounted volume, you might cause problems with
client apps, making the volume difficult to remount.
Set up a folder affinity
Every storage pool in a volume has an affinity tag. You can use the tag to be sure that
files in a folder are stored on a specific storage pool. Files in folders without affinities
are stored on the next available storage pool according to the volume’s allocation
strategy (fill, round-robin, or balance). For more information, see “Affinities and affinity
tags” on page 35 and “Folders with affinities” on page 36.
Some storage pools might be larger, faster, or better protected than others. Using
affinities, you can make sure that an app or task that needs speed or extra protection
stores its files on a suitable storage pool.