Replacing coordination points for server-based fencing in an online cluster
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Replacing coordination points for server-based fencing in an online cluster

Use the following procedure to perform a planned replacement of customized coordination points (CP servers or SCSI-3 disks) without incurring application downtime on an online client cluster.

Note   If multiple clusters share the same CP server, you must perform this replacement procedure in each cluster.

You can use the vxfenswap utility to replace coordination points when fencing is running in customized mode in an online cluster, with vxfen_mechanism=cps. The utility does not support migration from server-based fencing (vxfen_mode=customized) to disk-based fencing (vxfen_mode=scsi3) and vice-versa in an online cluster.

However, in a cluster that is offline you can migrate from disk-based fencing to server-based fencing and vice-versa:

• Disk-based to server-based fencing:

  Perform the tasks on the CP server and on the VCS cluster nodes as described in the "Enable fencing in a client cluster with a new CP server" scenario.

• Server-based to disk-based fencing:

  Perform the tasks on the VCS cluster nodes as described in the "Enable fencing in a client cluster with a new CP server" scenario.

See Deployment and migration scenarios for CP server

You can cancel the coordination point replacement operation at any time using the vxfenswap -a cancel command.

See About the vxfenswap utility

To replace coordination points for an online cluster

1. Ensure that the client cluster nodes and users have been added to the new CP server(s).

   This can be checked by running the following commands:

   # cpsadm -s cpserver -a list_nodes

   # cpsadm -s cpserver -a list_users

   If the client cluster nodes are not present here, prepare the new CP server(s) for use by the client cluster.

2. Ensure that fencing is running on the cluster using the old set of coordination points and in customized mode.

   For example, enter the following command:

   # vxfenadm -d

   The command returns:

   I/O Fencing Cluster Information:

   ================================

   Fencing Protocol Version: <version>

   Fencing Mode: CUSTOMIZED

   Cluster Members:

   * 0 (galaxy)

   1 (nebula)

   RFSM State Information:

   node 0 in state 8 (running)

   node 1 in state 8 (running)

3. Back up the /etc/vxfenmode file on each of the client cluster nodes.
4. Use a text editor to access /etc/vxfenmode and update the values to the new CP server (coordination points).

   The values of the /etc/vxfenmode file have to be updated on all the nodes in the VCS cluster.

   Review and if necessary, update the vxfenmode parameters for security, the coordination points, and if applicable to your configuration, vxfendg.

   Refer to the text information within the vxfenmode file for additional information about these parameters and their new possible values.

5. Run the vxfenswap utility from one of the nodes of the cluster.

   The vxfenswap utility requires secure ssh connection to all the cluster nodes.

   Use -n to use rsh instead of default ssh.

   # vxfenswap -n

6. If validation of coordination points from all the nodes fails, the vxfenswap utility rollbacks the coordination point replacement operation. Proceed to restore /etc/vxfenmode with the backed up file on all the VCS cluster nodes.
7. You are then prompted to commit the change. Enter y for yes.
8. Confirm the successful execution of the vxfenswap utility by checking the coordination points currently used by the vxfen driver.

   For example, run the following command:

   # vxfenconfig -l