VCS Q & A PAGE - 3

                 VCS INTERVIEW QUESTIONS AND ANSWERS
                                         
                                         PAGE - 3

 21..What is the difference between switchover and failover ?

Switchover is an manual task where as failover is automatic. You can switchover service group from online cluster node to offline cluster node in case of power outage, hardware failure, schedule shutdown and reboot. But the failover will failover the service group to the other node when VCS heartbeat link down, damaged, broken because of some disaster or system hung.

22..What is the use of hagrp command ?

hagrp is used for doing administrative actions on service groups like online, offline, switch etc.

23..How to switchover the service group in VCS ?

 hagrp –switch –to

24..How to online the service groups in VCS ?

 hagrp –online -sys

25..What is split brain in VCS?

Split brain occurs when all the LLT links fails simultaneously. Here systems in the cluster fail to identify whether it is a system failure or an interconnect failure. Each mini-cluster thus formed thinks that it is the only cluster thats active at the moment and tries to start the service groups on the other mini-cluster which he think is down. Similar thing happens to the other mini-cluster and this may lead to a simultaneous access to the storage and can cause data corruption.

 25..Where is the log file location in VCS?

#  /var/VRTSvcs/log/engine_A.log

27..What happens in case of a possible split brain?
A.. Both nodes think that the other node has failed and start racing to write their keys to the coordinator disks.
B. node01 manages to write the key to majority of disks i.e. 2 disks
C... node02 panics
D.. node01 now has a perfect membership and hence Service groups from node02 can be started on node01

28..Write the difference between freezing and  unfreezing groups?

Freeze a service group to prevent it from failing over to another system. This freezing process stops all online and offline procedures on the service group.

Unfreeze a frozen service group to perform online or offline operations on the service group.

29..How to freeze the service group?

#    hagrp -freeze service_group [-persistent]

The option -persistent enables the freeze to be remembered when the cluster is rebooted.

30..How to unfreeze the service group?

Hagrp –unfreeze service_group [-persistent]

31..Explain about critical and non critical?

 The Critical attribute for a resource defines whether a service group fails over when the resource faults.  is configured as non-critical (by setting the Critical attribute to 0) and no resources depending on the failed resource are critical, the service group will not fail over

32..How to check the VCS license?

#  vxlicense –p