Changing the CVM master manually


Changing the CVM master manually
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You can change the Cluster Volume Manager (CVM) master manually from one node in the cluster to another node, while the cluster is online. CVM migrates the master node, and reconfigures the cluster.

Symantec recommends that you switch the master when the cluster is not handling Veritas Volume Manager (VxVM) configuration changes or cluster reconfiguration operations. In most cases, CVM aborts the operation to change the master, if CVM detects that any configuration changes are occurring in the VxVM or the cluster. After the master change operation starts reconfiguring the cluster, other commands that require configuration changes will fail until the master switch completes.

See Errors during CVM master switching.

To change the master online, the cluster must be cluster protocol version 100 or greater.

To change the CVM master manually

To view the current master, use one of the following commands:

# vxclustadm nidmap
Name              CVM Nid    CM Nid    State
sys1            0 	        0         Joined: Slave
sys2            1          1         Joined: Master

# vxdctl -c mode
mode: enabled: cluster active - MASTER
master: sys2

In this example, the CVM master is sys2.

From any node on the cluster, run the following command to change the CVM master:
```
# vxclustadm setmaster nodename
```
where nodename specifies the name of the new CVM master.

The following example shows changing the master on a cluster from sys2 to sys1:
```
# vxclustadm setmaster sys1
```

To monitor the master switching, use the following command:

# vxclustadm -v nodestate 
 state: cluster member
        nodeId=0
        masterId=0
        neighborId=1
        members[0]=0xf
        joiners[0]=0x0
        leavers[0]=0x0
        members[1]=0x0
        joiners[1]=0x0
        leavers[1]=0x0
        reconfig_seqnum=0x9f9767
        vxfen=off
state: master switching in progress 
reconfig: vxconfigd in join

In this example, the state indicates that the master is being changed.

To verify whether the master has successfully changed, use one of the following commands:

# vxclustadm nidmap
Name              CVM Nid    CM Nid    State
sys1            0 	        0         Joined: Master
sys2            1    	     1         Joined: Slave

# vxdctl -c mode
mode: enabled: cluster active - MASTER
master: sys1

Errors during CVM master switching

Symantec recommends that you switch the master when the cluster is not handling Veritas Volume Manager (VxVM) or cluster configuration changes.

In most cases, Cluster Volume Manager (CVM) aborts the operation to change the master, if CVM detects any configuration changes in progress. CVM logs the reason for the failure into the system logs. In some cases, the failure is displayed in the vxclustadm setmaster output as follows:

# vxclustadm setmaster sys1
VxVM vxclustadm ERROR V-5-1-15837 Master switching, a reconfiguration or 
a transaction is in progress. 
Try again

In some cases, if the master switching operation is interrupted with another reconfiguration operation, the master change fails. In this case, the existing master remains the master of the cluster. After the reconfiguration is complete, reissue the vxclustadm setmaster command to change the master.

If the master switching operation has started the reconfiguration, any command that initiates a configuration change fails with the following error:

Node processing a master-switch request. Retry operation.

If you see this message, retry the command after the master switching has completed.

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