Changing the master metadata server

This topic describes how to change which server in the SAN File System cluster serves as the master.

Prerequisites

You must have Operator or Administrator privileges to perform this task.

Before this task can be performed, the current master server must be down, but the cluster must be up. Additionally, the engine hosting the master server must be powered off. The subordinate server that will become the master must be in the “joining” or “forming” state only.
Remember: Before you shutdown the current master server, move the filesets that the current master server is serving to a subordinate server.

Context

This task can be performed only at the administrative command-line interface. You may need to convert a subordinate server to the master server in the event of an irrecoverable loss of the original cluster master server. Such a loss might be due to hardware failures, software failures, or partitioned networks.

Steps

  1. Go to the administrative command-line interface.
  2. Make sure the cluster does not have a master metadata server: In the SAN File System console, if the master engine is running, you can check the Servers panel to make sure the master metadata server is down.
    Restriction: If the master engine is not up, the SAN File System console will not work.
  3. In certain failure scenarios it is possible, but unlikely, that the SAN File System console is not working, but the master metadata server is still up. You can try to log in to the operating system on the engine hosting the master metadata server and use the lsserver and a stopserver commands if necessary. In this scenario it is likely that the administrative command-line interface on the master engine also does not work, in which case, you should shut down the engine as described in a following step.
  4. On the subordinate engine that you want to make the new master, a subordinate metadata server must be running. Log in to the operating system on this engine and use the lsserver command to see if a local subordinate metadata server is running. If not, using the startserver command on this engine starts the subordinate metadata server.
  5. Next, make sure the engine that was hosting the master metadata server is shut down:
    1. Use the lsengine master_metadata_server command to determine if the engine hosting the master metadata server is running.
    2. Use the stopengine master_metadata_server command to shut it down.
      Tip: You might need to use -f flag if the engine is hung. Use lsengine again to ensure it is down.
  6. In the unlikely case that the failure is severe enough that these commands are not working, you must manually power off the engine that was hosting the master, and manually reboot the engine that you want to become master. Then return to step 4.
  7. Enter the setmaster command and the name of the server that you want to assign master status. You can test the success of this action by using the lsserver command. Once this step is successful, the SAN File System console will work.
    Attention: If you receive note of an internal error after performing this operation, please contact your IBM Support personnel.

Postrequisites

After issuing the setmaster command, you must manually edit the tank.properties file on the subordinate server that will become the master and set the IsMaster property to true.

Parent topic: Managing metadata servers

Related concepts
Cluster
Metadata server
User roles

Related tasks
Powering on the engine
Powering on the engine

Related reference
Servers panel
lsengine
Metadata server states
startserver
stopengine
stopserver

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