It is possible to avoid tie breaker disk in pureScale and HADR just by following a simple majority rule.
You need a tie breaker disk in pureScale and HADR if number of hosts are even.
So, in HADR you have only two nodes so your need a tie breaker disk. But, even in HADR, I can use any highly available machine on the network and just install TSA (using installSAM) command) on it and add that machine to the peer domain and use majority as a tie breaker.
The commands are simple:
HADR with a arbitrator Node
Say, you have node01, node02 as HADR pair and a 3rd machine as a highly available machine (say in IBM cloud or others – outside the data centers) but make sure that it is available all the time.
Assume that HADR pair is up and running with TSA configured for automated failure. But, sometime getting a tie-breaker disk may not be available in 2 data center strategy – so get a simple cheapest machine on cloud and use that machine to convert the peer domain in odd numbers so that majority can be used to grant the operational quorum to the host and still avoid split brain situation when node01 and node02 are up but not talking to each other. [Note: If you have ping latency more than 10 ms, it is not a good idea to use Cloud based arbitrator node but you could still use cloud based disk tie-breaker as defined in this: https://ibm.biz/Bd4mSK
node01> prepprnode node03
node02> preprnode node03
node03> prepprnode node01 node02 node03
node01> addrpnode node03
node01> lsrpnode –> you should see node03 as offline
node01> startrpnode node03
lssam –> find out the name of the network equivalency. For example, in our case it is db2_private_network_0
node01> chequ -u a db2_private_network_0 IBM.NetworkInterface:eth0:node03
Replace eth0 with the public IP address interface that you have on your machine. And you are done by setting up a majority tie-breaker.
pureScale Majority Tie-Breaker
In pureScale, you do not need a tie-breaker if you have odd-number of nodes such as 3, 5, 7 etc.
For example, if you have a 3 db2 member node cluster with 2 CFs. Just don’t bother about setting up a tie breaker disk. Use the following command.
# db2cluster -cm -set -tiebreaker -majorty
And, you are done.