Multipathing Overview for XenServer

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Information

This article provides a general overview of multipathing on Citrix XenServer 5.0.

Contents

Basic multipath configuration

Advanced multipath configuration

iSCSI testing and troubleshooting commands

Fibre Channel (FC) testing and troubleshooting commands

FAQ

Basic Multipath Configuration

There are three cases for multipathing implementation:

• You do not have existing Storage Repositories (SRs), you only have local SRs
• You have existing SRs on the host running in single path
• You have existing SRs and you upgraded from Xen Server 4.1 to 5.0

You do not have existing SRs, you only have local SRs:

GUI Instructions

1. In XenCenter, select Enter Maintenance Mode on the server, as displayed in the following screen shot:
   

2. Enable multipathing. To do so, open the server's Properties page, select the Multipathing tab, and select Enable multipathing on this server.
   

3. Exit Maintenance mode.

4. Repeat Steps 1, 2, and 3 on each XenServer in the pool.

5. Now you can create new SRs. New SRs should go over multiple paths automatically.

CLI Instructions

1. Run the following command to set the host's other-config:multipathing parameter:
   # xe host-param-set other-config:multipathing=true uuid=host_uuid

2. Set the host's other-config:multipathhandle parameter to dmp:
   # xe host-param-set other-config:multipathhandle=dmp uuid=host_uuid

3. Repeat Steps 1 and 2 on each server in the pool.

4. Now you can create new SRs. New SRs should go over multiple paths automatically.

You have existing SRs on the host running in a single path:

GUI Instructions

1. Stop all Virtual Machines running out of the SRs.

2. Unplug the Physical Block Devices (PBDs) related to such SRs for safety purposes.

3. Find the PBD related to particular storage:
   # xe sr-list uuid=<sr-uuid> params=all

4. Unplug the PBD:
   # xe pbd-unplug uuid=<pbd_uuid>

5. Enter Maintenance mode on the server.
   

6. Enable multipathing.
   

7. Exit the Maintenance mode.

8. Repeat Steps 5, 6, and 7 on each server in the pool.

9. Repair the storage.

CLI Instructions

1. Stop all Virtual Machines running out of the SRs.

2. Unplug the PBDs related to such SRs for safety purposes.

3. Find the PBD related to particular storage:
   # xe sr-list uuid=<sr-uuid> params=all

4. Unplug the PBD:
   # xe pbd-unplug uuid=<pbd_uuid>

5. Set the host's other-config:multipathing parameter:
   # xe host-param-set other-config:multipathing=true uuid=host_uuid

6. Set the host's other-config:multipathhandle parameter to dmp:
   # xe host-param-set other-config:multipathhandle=dmp uuid=host_uuid

7. Repeat steps 5 and 6 on each server in the pool.

8. Plug the PBD in:
   # xe pbd-plug uuid=<pbd_uuid>

You have existing SRs on the host and you upgraded from XenServer 4.1 to 5.0 (Fibre Channel):

After upgrading XenServer to version 5.0, you might notice that your Fibre Channel (FC) storage (type=lvmohba) is broken and you are unable to repair it.

Complete the following procedure to fix this issue:

1. Take note of the Logical Unit Number (LUN) ID related to the particular SR that you want to fix.
   # xe sr-list uuid=<sr-uuid> params=all
   (this will display your PBD Universally Unique Identifier (UUID))
   # xe pbd-list uuid=<pbd-uuid_from_previous_command> params=all
   Note the device-config parameter that includes the SCSI ID.
   (device-config (MRO): device: /dev/mapper/360a9800050334c66435a4c3046675242)

2. Using the GUI, detach the storage repository, as displayed in the following screen shot:
   

3. Reattach the storage repository.
   

4. The wizard might offer you many LUNs to reattach. Choose the one with appropriate SCSI ID that you gathered in Step 1.
   
   

5. Click Yes to reattach the SR.

6. Repeat Steps 1, 2, and 3 for every FC storage that is broken after the upgrade.
   Note: If you do not see the storage properly attached, run the following command:
   # xe-toolstack-restart
   Or
   Disconnect and reconnect the pool in XenCenter.

7. Select Enter Maintenance mode on the server.
   

8. Enable multipathing.
   

9. Exit Maintenance mode.

10. Repeat Steps 7, 8, and 9 on each server in the pool.

11. You should be able to see the storage attached with multiple paths in XenCenter.
    

Advanced Multipath Configuration

You must edit the /etc/multipath-enable.conf file on each XenServer host in the pool. The file must be the same across the pool.