Xsan Help: Tips to avoid unexpected volume behavior

An Xsan Volume Can't Be Renamed in the Finder

You can't change the name of a mounted Xsan volume using the Finder. If you try, you get a message saying the name you've typed cannot be used, even if it is an acceptable Xsan volume name.

To rename an Xsan volume, you must use Xsan Admin to reinitialize the volume.

Instructions for renaming an Xsan volume are on page 52 of the "Xsan Administrator's Guide."

Ignore Finder Initialization Dialog for Xsan LUNs

After you create a new, uninitialized LUN (by using RAID Admin to create an array on an Xserve RAID system, for example), you may see the following message on a computer connected to the LUN:

"You have inserted a disk containing no volumes that Mac OS X can read. To continue with the disk inserted, click Ignore."

Click the Ignore button. Don't use the Finder to initialize the LUN. You'll initialize the LUN for use with Xsan when you add it to a storage pool using Xsan Admin.

Unmount Xsan Volumes Before Reconfiguring SAN

Breaking the Fibre Channel connection between an Xsan client and a mounted volume for more than one minute causes the volume to be unmounted from the client in a way that can cause problems with applications running on the client and make the volume difficult to remount.

If you need more than a minute to reconfigure your SAN:

First unmount Xsan volumes from all client computers and controllers, then either shut down all computers connected to the SAN or disconnect their Fibre Channel cables.

Problems Starting a Volume After Adding LUNs or Storage Pools

If you can't restart a volume after you add LUNs or storage pools, you can follow the steps below to return the volume to its previous state.

To return a modified volume to its previous configuration:
1. Quit Xsan Admin.
2. Delete the file /Library/Filesystems/Xsan/config/.cfg from each of the volume's controllers.
3. On each controller, rename the volume's previous configuration file /Library/Filesystems/Xsan/config/.cfg.backup to /Library/Filesystems/Xsan/config/.cfg.
4. Open Xsan Admin and start the volume.

This should return the volume to the state it was in before you tried to expand it.

Using Non-Redundant LUNs Puts Volumes at Risk

If a LUN belonging to an Xsan volume suffers a failure and can't be recovered, all data on the volume is lost. It is strongly recommended that you use only redundant LUNs (LUNs based on RAID schemes other than RAID 0) to create your Xsan volumes.

LUNs configured as RAID 0 arrays (striping only) or LUNs based on single drives are difficult or impossible to recover if they fail. Unrecoverable LUNs such as these should only be used for volumes that contain scratch files or other data that you can afford to lose.

Xserve RAID systems ship already configured as recoverable, redundant RAID 5 arrays.

How Xsan Admin Calculates Volume Storage Capacity

When reporting the size of a volume, Xsan Admin does not include space on storage pools that are set to contain only journal data and metadata. Only space on storage pools where users can store data (that is, storage pools set to be used for "Any data" or "User data only") is counted.

For example, if you create a volume consisting of four 120 gigabyte (GB) storage pools, one of which is designated for journal and metadata only, Xsan Admin reports the size of the volume as 360 GB, not 480 GB.

Unmount Volumes Before Expanding Them

Before you add LUNs or storage pools to an existing volume to increase its capacity, unmount the volume from all clients and controllers and stop the volume. After you have saved the expanded volume configuration in Xsan Admin, you can mount the volume again.

To expand a volume:
1. Unmount the volume from all clients and controllers. (Open Xsan Admin, select the volume, click Clients, select computers, and click Unmount.)
2. Stop the volume. (In Xsan Admin, select the volume and click Stop Volume.)
3. Add LUNs or storage pools. (In Xsan Admin, select the SAN or controller, click Setup, and click Storage.)
4. Start the volume.
5. Mount the volume on clients and controllers.

IMPORTANT: If you forget to unmount a volume from a client (step 1) before you stop it (step 2), be sure to click Disconnect in the "server no longer available" dialog that appears on the client.

Note: You can't add LUNs to a storage pool that contains journal data or metadata. To see how a storage pool is used, open Xsan Admin, select the volume, click Setup, and click Storage. Then double-click the storage pool and look next to "Use for" in the storage pool information sheet. If the storage pool is set to "User data only" you can add LUNs to it. If it is set to "Any data" or "Journaling and metadata only" you cannot expand it.

Unmount Volumes Before Restarting a Controller

Before you restart an Xsan controller, unmount all Xsan volumes on the controller.

To unmount a volume on a controller:

Open Xsan Admin and select a volume in the San Components list. Click Clients, select the controller in the list of clients, and click Unmount.

You don't need to unmount the volume on other clients, only on the controller that you are restarting.

After unmounting the volume, you can restart the controller.

Trouble Emptying the Trash

If you have trouble emptying the trash of files you've deleted from an Xsan volume, it might be because the volume doesn't have a storage pool available for general use (that is, all storage pools in the volume are configured to be used exclusively for either journal data and metadata only or user data with affinity only).

Every volume should include a storage pool that is available for non-exclusive use (a storage pool that is configured to be used for either "Any data" or "User data only").

Don't Mount a Volume Until Startup Finishes

Don't mount an Xsan volume on any clients until the volume has finished starting up.

When you click Start Volume, a spinning activity indicator appears in the upper-right portion of the Xsan Admin window to indicate that the volume is starting up. Don't click Mount Read & Write or Mount Read Only on the Clients tab until after the activity indicator disappears and the Stop Volume button is activated at the top of the window.

"Disk is Full" Message for a Volume With Free Space

If you see the warning message "The operation cannot be completed because the disk is full" when you try to copy a file or folder to an Xsan volume that has free space, it's probably because the volume doesn't include a storage pool that is available for general use (that is, all storage pools in the volume are configured to be used exclusively for either journal data and metadata only or user data with affinity only).

Every volume you set up should include at least one storage pool that is available for non-exclusive use (a storage pool that is configured to be used for either "Any data" or "User data only," but not "Only data with affinity").

To check the data types a storage pool can be used for:
1. Open Xsan Admin, select the SAN or controller, and click Setup.
2. Click Storage, then double-click the storage pool in the list. Look next to "Use for" in the storage pool settings sheet to see how the storage pool is used.