This section describes the reasons, benefits, considerations, and the procedure to set the order of the existing coordination points using the web-based installer.
It does not apply to majority-based I/O fencing.
You can decide the order in which coordination points can participate in a race during a network partition. In a network partition scenario, I/O fencing attempts to contact coordination points for membership arbitration based on the order that is set in the vxfenmode
file.
When I/O fencing is not able to connect to the first coordination point in the sequence it goes to the second coordination point and so on. To avoid a cluster panic, the surviving subcluster must win majority of the coordination points. So, the order must begin with the coordination point that has the best chance to win the race and must end with the coordination point that has the least chance to win the race
For fencing configurations that use a mix of coordination point servers and coordination disks, you can either specify coordination point servers before coordination point disks or disks before servers.
Considerations to decide the order of coordination points
Choose coordination points based on their chances gain membership on the cluster during the race and hence gain control over a network partition. In effect, you have the ability to save a partition.
First in the order must be the coordination point that has the best chance to win the race. The next coordination point you list in the order must have relatively lesser chance to win the race. Complete the order such that the last coordination point has the least chance to win the race.
To set the order of existing coordination points for server-based fencing using the web-based installer
Click Next.
The installer performs the initial system verification. It checks for the system communication. It also checks for release compatibility, installed product version, platform version, and performs product prechecks.
Click Yes.
Set the order of existing coordination points
option.Installer prepares the vxfenmode
file on all nodes and runs the vxfenswap utility to update the new order of coordination points.
Click Finish.