Xsan 2 Administrator Guide - Adding LUNs to a Storage Pool

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Adding LUNs to a Storage Pool

You can increase the size of a SAN volume by adding LUNs (RAID arrays or array slices)
to storage pools in the volume. If you’re expanding a volume that is based on a built-
in volume type, you add LUNs to affinity tags and Xsan Admin assigns those LUNs
to underlying storage pools for you, creating storage pools as needed, based on the
optimal number of LUNs per pool for the volume type (“Assigning LUNs to Affinity
Tags” on page 29). If you’re expanding a custom volume, you add LUNs directly to
storage pools.

Note: A storage pool can’t contain more than 32 LUNs, the total number of LUNs in
a volume can’t be greater than 512, and you can’t add LUNs to a storage pool that
contains only journal data or metadata.

Choosing Compatible LUNs
LUNs you add to an existing storage pool must be at least as large as the LUNs in the
pool. On the other hand, if a new LUN is larger than the other LUNs in the pool, its
extra capacity can’t be used. Always try to add LUNs that are identical or similar in
performance and capacity to the LUNs already in the storage pool. Mixing LUNs of
different sizes or speeds in the same storage pool wastes capacity and can degrade

Action menu

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To add a LUN to a storage pool:


If you haven’t already done so, connect the RAID system that hosts the LUN to the SAN

Fibre Channel network and power on the device.


In Xsan Admin, select Volumes in the SAN Assets list.


Select the volume in the list and choose Expand Volume from the Action (gear) pop-

up menu.


In the Label LUNs pane of the assistant, choose whether you want to label unlabeled

LUNs individually or sequentially based on a label prefix.
If you use a label prefix, Xsan Admin adds a number to the end of the prefix to create
a label for each LUN. For example, if you use the prefix “LUN,” your LUNs are labeled
“LUN1,” “LUN2,” and so forth. Already labeled LUNs aren’t affected.
If you label LUNs individually, click Edit LUN Label on the next pane and enter a
new label.
If your LUNs are already labeled, they aren’t changed.


In the Configure Volume Storage pane, drag the new LUNs to affinity tags (or storage

pools, if this is a custom volume).


Click Continue to unmount and stop the volume, add the storage, and remount the

expanded volume.

For best performance, defragment the volume after adding LUNs to a storage pool so
that files are striped efficiently across all LUNs.

From the Command Line
You can also add LUNs to a storage pool by modifying the associated volume
configuration file and using the


command in Terminal. For more information,

see the




man pages (

% man -M /Library/Filesystems/

Xsan/man/ 4 cvfs_config

) or “Xsan Configuration Files” on page 122 and “Labeling,

Listing, and Unlabeling LUNs (cvlabel)” on page 116.