How to add a low or high priority heartbeat to the cluster configuration without affecting online VCS resources.

The issue:

An additional heartbeat link is desired for additional redundancy of the cluster heartbeats.



To resolve the issue:

The Low Latency Transport (LLT) reads the /etc/llttab file when started.

Upon LLT startup, the proper devices for Low Latency Transport to monitor are loaded from the /etc/llttab file.

It is possible to change the devices that Low Latency transport monitors while it is active.

To add a new high priority link (private heartbeat) while Low Latency transport is active, use the following command on each node: 

Syntax-

lltconfig -t <alias> -d <device> -b ether



For example-

It is desired to add a private heartbeat link on the interface qfe:4.

The link may be added with the following command on each node.

# lltconfig -t qfe4 -d /dev/qfe:4 -b ether



To add a new low priority link (utilizing a public interface), use the following command on each node:

Syntax-

lltconfig -t <alias> -l -d <device> -b ether



Example using qfe4 again for a low-pri link:

# lltconfig -t qfe4 -l -d /dev/qfe:4 -b ether

Note the "-l" (lowercase letter 'L') after <alias> is the parameter to define the new heartbeat connection as a low-priority connection.

Note also, that "low-priority" connections are not recommended for use in Oracle RAC clusters for data security reasons.



The commands above add a link to the running configuration.

An additional change to the file "/etc/llttab" must be made on each node to make the change a permanent change to the configuration of the cluster.

The process for the permanent change will be explained later in this document.



Once the heartbeat is added, the new link configuration can be verified with the following command: 

# lltstat -vvn 

The newly configured link will show in the output. 



Additionally, to determine / verify whether links are "high priority" (private), or "low-priority" (public), use the following command:

# lltstat -l |grep link

Example output:

# lltstat -l |grep link

link 0 qfe2 on etherfp hipri

link 1 qfe3 on etherfp hipri

link 2 qfe4 on etherfp lowpri



The process to make the change to the cluster configuration permanent follows.

Here is an example /etc/llttab configuration with two Private Heartbeat Links.

# cat /etc/llttab

set-node testnode1

set-cluster 100

link qfe2 /dev/qfe:2 - ether - -

link qfe3 /dev/qfe:3 - ether - -



Use "vi" or a similar editor to perform a manual change to the "/etc/llttab" file on each node.  

If a high priority (private) link on qfe4 is desired, an additional line is added to the end of the links listed in the file, as shown below: 

Again, the example uses qfe4.

# cat /etc/llttab

set-node testnode1

set-cluster 100

link qfe2 /dev/qfe:2 - ether - -

link qfe3 /dev/qfe:3 - ether - -

link qfe4 /dev/qfe:4 - ether - -



If a low priority (public) link on qfe4 is desired, a line would be added as follows in this example:

# cat /etc/llttab

set-node testnode1

set-cluster 100

link qfe2 /dev/qfe:2 - ether - -

link qfe3 /dev/qfe:3 - ether - -

link-lowpri qfe4 /dev/qfe:4 - ether - -

Note the "low-pri" designation for this link.



Upon reboot of the system, the VCS configuration will read the additional link that was added to "/etc/llttab" in either of the above steps.

The change to the link configuration is now permanent.

Credit to :-https://www.veritas.com/