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Home / Interview Questions / Veritas cluster Interview Questions-2

Veritas cluster Interview Questions-2

April 25, 2013

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in Interview Questions, VCS, VCS-Interview Questions

Lingeswaran R

Veritas clusterinterviewquestions & answers part 2 will help you to overcome from L3 level VCS interview which will
be asked frequently for SME position across many organizations.
Here is the Top:30 VCS interview questions for you.
Please go through questions andanswers. Let me know if you have any doubt by leaving comment.
Adding and removing cluster node
Q1 How to add a node in an existing cluster?
Ans: Adding a node into an existing cluster is a multi steps process.
1: Set up the hardware
Before adding a node to an existing cluster, node must be physically connected with the cluster.
1: Connect the VCS private Ethernet controllers
2: Connect the node to the shared storage

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2: Install the VCS software in the node

Install the VCS software and install the license.

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3: Configure LLT and GAB

Create the LLT & GAB configuration files (/etc/llthosts, /etc/llttab and /etc/gabtab) in the new node and update the
files on the existing node.
4: Add the node to an existing cluster
We have to perform below given tasks in any of the existing node of a cluster
1:Make to cluster configuration R/W
# haconf makerw

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2:Add the new node to the cluster

# hasys add <new node name>
3:Copy main.cf file from an existing node to new node
# scp /etc/VRTSvcs/conf/config/main.cf new_node:/
/etc/VRTSvcs/conf/config/main.cf

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4:Start vcs on the new node

# hastart

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5:Now make the configuration again read only.

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5: Start VCS and verify the cluster

1:Start VCS on the new node
# hastart

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6: Run the GAB configuration command on each node to verify that port a and port h include the new node
in the membership.
# /sbin/gabconfig a

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Q2 How to remove a node from an existing cluster?

Ans: Removing a node from a cluster includes many steps, which are given below:
1: Backup the configuration file
# cp /etc/VRTSvcs/conf/config/main.cf /etc/VRTSvcs/conf/config/main.cf.orig
2: Check the status of the nodes and the service groups

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# hastatus summary

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3: Switch service group which is online on the node leaving the cluster
# hagrp switch <service group> to <node name>
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4: Delete the node from the VCS configuration

1: Make the cluster configuration R/W
# haconf makerw
2: Stop the cluster on leaving node
# hastop sys <node>

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3: Delete the leaving node from the service groups SystemList attribute.
# hagrp modify <group> SystemList delete <node>
4: Delete the node from the cluster
# hasys delete <node>
5: Now again make the cluster configuration Read Only.
# haconf dump makero
5: Modify the LLT and GAB configuration files to reflect changes
Modify /etc/llthosts, /etc/llttab and /etc/gabtab files on the remining node on the cluster.
6: Remove VCS configuration on the node leaving the cluster
1: Unconfigure and unload LLT and GAB
# /sbin/gabconfig U
# /sbin/lltconfig U

2: Unload the LLT and GAB modules

# modunload i <gab_module>
# modunload I <llt_module>

3:

Rename the startup files to prevent LLT, GAB and VCS from
starting up in future.
# mv /etc/rc2.d/S70llt /etc/rc2.d/s70llt
# mv /etc/rc2.d/S92gab /etc/rc2.d/s92gab
# mv /etc/rc3.d/S99vcs /etc/rc3.d/s99vcs

4: Remove VCS package from the node

Some General Questions:

Q1 How to shutdown a node in VCS cluster?
Ans: Shutting down a VCS node is multi step process.

1) Make the cluster configuration Read/Write

# haconf makerw
2) Either Switchover or failover all the service group which are online on shutting down node to remaining node
# hagrp switch <service group> to <node name>
3) Freeze all the service group which are online in the cluster.
# hagrp freeze <service group> persistent

4) Stop the cluster on the node that is going to be down.

# hastop local force
5) Rename the VCS startup script
# cd /etc/rc3.d
# mv S99vcs s99vcs
6) Now reboot the box.
Once the system will come up after reboot, Follow the below given instructions.
1) Start the VCS on this node
# hastart force
2) Make the service group online if they were made offline before the system down.
# hagrp online <service group> sys <node name>
3) Unfreeze all the service groups which are frozen.
# hagrp unfreeze <service group> persistent
4) Now make the cluster configuration ReadOnly
# haconf dump makero
5) Now again move back the VCS startup script

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# cd /etc/rc3.d
# mv s99vcs S99vcs
Q2 How do check the status of VERITAS Cluster Server?
Ans: hastatus sum
Q3 Which is the main config file for VCS and where it is located?
Ans: main.cf is the main configuration file for VCS and it is located in /etc/VRTSvcs/conf/config.
Q4 Which command you will use to check the syntax of the main.cf?
Ans: hacf verify /etc/VRTSvcs/conf/config
Q5 How will you check the status of individual resource of VCS cluster?
Ans: hares state <resource>
Q6 What is the service group in VCS?
Ans: Service group is made up of resources and their links which you normally requires to maintain the HA of
application.
Q7 What is the use of halink command?
Ans: halink is used to link the dependencies of the resources
Q8 What is the difference between switchover and failover?
Ans: 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.
Q9 What is the use of hagrp command?
Ans: hagrp is used for doing administrative actions on service groups like online, offline, switch etc.
Q10 How to switchover the service group in VCS?
Ans: hagrp switch <service group> to <node>
Q11 How to online the service groups in VCS?
Ans: hagrp online <service group> sys <node>
Q12 How to access the VCS cluster management console?
Ans: VCS cluster management console can be accessed by the below given URLs:
http://Servername:8181/cmc/
or
https://Servername:8443/cmc
Q13 How to access the Cluster Manager Java Console?
Ans: #/opt/VRTSvcs/bin/hagui
Q14 What is Jeopardy?
Ans: When a node in the cluster is having only one interconnected link remaining, then its very difficult for GAB to
discriminate between system or network failure. A special membership category takes effect in this situation, called
jeopardy membership. This memebship prevent cluster from split brain condition. When a system is placed in jeopardy
membership, two actions occur:
1: Service groups running on this node placed in auto disabled state. A service group in auto disabled state may
failover on a resource or group fault but cant failover on system fault.
2: VCS operates the cluster as a single node cluster. Other systems in the clusters are partitioned off in a separate
cluster membership.

Q15 What is the main daemon of VCS?

Ans: had (high availability daemon) which is started by hashadow daemon.
Q16 What is GAB?
Ans: Group Membership Services/Atomic Broadcast (GAB) is responsible for cluster membership and reliable cluster
communication. GAB has two major functions:
1: Cluster membership
GAB maintains cluster membership by receiving heartbeat from LLT. When a system no longer receives heartbeats
from a cluster peer, GAB marks the node as down.
2: Cluster communication
GAB provides the guranteed delivery of messages to all the systems. The atomic broadcast functionality is used by HAD
to ensure that all systems within the cluster receive configuration change messages.
Q17 What is LLT?
Ans: Low Latency Transport (LLT) is used for all cluster communication. LLT has 2 major functions:
1: Traffic Distribution
LLT works as a backbone for GAB. LLT distributes all inter communication across all configured network links. If a link
is failes, traffic is directed to the remaining link.
2: Heartbeat
LLT is responsible for sending and receiving heartbeat signals.

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Q18 How many network links are supported in LLT?

Ans: 8 links are supported.
Q19 How many nodes can join a Cluster?
Ans: Maximum of 32 nodes is supported in VCS.
Q20 What is heartbeat?
Ans: Heartbeat is an Ethernet broadcast packet. This packet notifies all othe nodes that sender is functional. This is
the only broadcast traffic generated by VCS. Each node sends 2 hearbeat packets per second per interface. Heartbeat
is used by GAB to determine cluster membership.
Q21 What is split brain condition?
Ans: When all the cluster interconnected links fail, it is possible for one cluster to separate into 2 subclusters, each of
which doesnt know about the other subcluster. The two subclusters could each carry out recovery actions for the
departed system. For example two systems could try to import the same storage and cause data corruption.
Q22 How do you shutdown a Veritas Cluster Server, leaving the applications running from the command line?
Ans: # hastop all forceQ23 What is coordinator disk?
Ans: Coordinator disks are three standard disks or LUNs set aside for I/O fencing during cluster reconfiguration.
Coordinator disks do not serve any other storage purpose in the VCS configuration. These disks provide a lock
mechanism to determine which nodes get to fence off data drives from other nodes. A node must eject a peer from
the coordinator disks before it can fence the peer from the data drives. This concept of racing for control of the
coordinator disks to gain the ability to fence data disks is key to understanding prevention of split brain through
fencing.

Q24 What is IO fencing and how to configure IO fencing?

Ans: IO fencing is a feature that prevents data corruption in the event of a communication breakdown in a cluster. IO
fencing is used to remove the risk associated with split brain condition. I/O fencing allows write access for members of
the active cluster and blocks access to storage from nonmembers; even a node that is alive is unable to cause
damage.
Q25 How to upgrade VCS?
Ans:
1) Removing the deprecated resource type
2) Start the installvcs program which is under the directory cluster_server
Q26 How to perform minimal downtimeupgradationin VCS?

Q27 How to upgrade Solaris OS in which VCS is running?

Ans: To upgrade a Solaris OS in which VCS is running, Follow the below instruction:
1) Stop VCS on this node
Make the VCS configuration R/W
# haconf makerw
Move all service groups from this node to another node and freeze this node:
# hasys freeze persistent evacuate <node name>
# Make the cluster configuration Read/Only?
# haconf dump makero
# Stop the cluster on this node
# hastop force local
2) Stop, unconfigure and unsinstall LLT and GAB on this node
Unconfigure GAB
# gabconfig U
Unconfigure LLT
# lltconfig U
Now remove GAB and LLT packages
# pkgrm VRTSgab VRTSllt
3) Now upgrade Solaris and switch to single user mode
4) Now Install and configure LLT and GAB
# pkgadd d . VRTSgab VRTSllt
5) Now switch to multi user mode and start VCS
# init 3
# hastart
6) Now unfreeze this node
# hasys unfreeze persistent <node name>

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# haconf dump makero

Thank you for reading this article. Feel free to checkVCSinterview questions part1 for basic VCS Q&A.

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