Today, in the 3d party of my “In a nutshell” story I`ll talk about VmWare High Availability: what it is, and how does it work.
HA cluster can consist maximum of 32 servers, while 5 of them will be primary nodes. Primary nodes are keeping information about current configuration, and synchronize it between each other. If cluster includes less than 5 nodes, all of them will be primary.
By default hearbeat are sent primary-primary and secondary-primary every second, but you can change this parameter by command das.failuredetectioninterval.
First 5 nodes in cluster are primary, while all the rest – secondary. Both active, and passive servers are chosen randomly. The only way to see which servers are primary is to type the following command into service console:
cat /var/log/vmware/aam/aam_config_util_listnodes.log
or
/opt/vmware/aam/bin/Cli (ftcli on earlier versions).
AAM> ln
If one of primary hosts goes down, re-selection (one of secondary nodes becomes primary) doesn`t happen. It happens only if primary node goes to maintenance mode, if it`s disconnected or deleted from cluster.
One of primary hosts is Active Primary – it regulates reboot of VMs. If it goes down, another server will be assigned with this role. If all 5 primary servers go down - there will be no reboot of VMs, HA requires at least one active server for its work.
That`s all for today! Thanks and bye!