Q: – What is a Veritas Cluster server or VCS cluster ?
VERITAS Cluster Server (VCS) from Symantec connects multiple, independent systems into a management framework for increased availability. Each system, or node, runs its own operating system and cooperates at the software level to form a cluster. VCS links commodity hardware with intelligent software to provide application failover and control. When a node or a monitored application fails, other nodes can take predefined actions to take over and bring up services elsewhere in the cluster.
Q: – What are types of cluster ?
Cluster is an broadly used term and broadly classified as
– High Availability (HA) clusters
– Parallel processing clusters
– Load balancing clusters
High Performance Computing (HPC) clusters
VCS is primarily an HA cluster
–With support for some key parallel processing applications like Oracle RAC
Q: – What are Veritas Cluster or VCS User Account Privileges ?
Cluster Administrator:- Full Privileges
Cluster Operator:- All cluster, service group, and resources-level operations.
Cluster Guest :- Read-only access: new users created as cluster guest accounts by default.
Group Administrator :- All service group operations for a specified service group,except deleting service group.
Group Operator :- Bring service groups and resources online and take offline, temporarily freeze or unfreeze service groups
Q: – What are SwitchOver and Failover in Veritas Cluster ?
Switchover: A switchover is an orderly shutdown of an application and it’s supporting resources on one server and a controlled startup on another server.
Failover : A failover is similar to a switchover, except the ordered shutdown of applications on the original node may not be possible, so the services are started on another node.
Q: – Definition of a Service Group in Veritas Cluster ?
A service group is a virtual container that enables VCS to manage an application service as a unit.All components required to provide the service, and the relationships between these components, are defined within the service group.Service groups have attributes that define its behavior, such as where it can start and run.
Q: – What are Service Group Types ?
– The service group can be online on only one cluster system at a time.
– VCS migrates the service group at the administrator’s request and in response to faults.
The service group can be online on multiple cluster systems simultaneously.
An example is Oracle Real Application Clusters (RAC).
Q: – How to specify Service Group Dependencies in veritas Cluster ?
We can use service group dependencies to specify most application relationships according to these four criteria:
– Category: Online or offline
– Location: Local, remote, or global
– Startup behavior: Parent or child
– Failover behavior: Soft, firm, or hard
We can specify combinations of these characteristics to determine how dependencies affect service group behavior.
Q: – Define the Resources in veritas cluster ?
Resources are VCS objects that correspond to the hardware or software components of an application service.
- Each resource must have a unique name throughout the cluster. Choosing names that reflect the service group name makes it easy to identify all the resources in that group, for example, WebIP in the WebSG group.
- Resources are always contained within service groups.
- Resource categories include: Persistent & Nonpersistent
Q: – What are On-Off & Persistent Resources ?
On-Off:- VCS starts and stops On-Off resources as required. For example, VCS imports a disk group when required, and deports it when it is no longer needed.
Persistent:- These resources cannot be brought online or taken offline. For example, a network interface card cannot be started or stopped, but it is required to configure an IP address. A Persistent resource has an operation value of none. VCS monitors Persistent resources to ensure their status and operation. Failure of a Persistent resource triggers a service group failover.
Q: – What are Agents in Veritas cluster or VCS cluster ?
Agents are multi-threaded processes that provide the logic to manage resources. VCS has one agent per resource type. The agent monitors all resources of that type; for example, a single IP agent manages all IP resources. When the agent is started, it obtains the necessary configuration information from VCS. It then periodically monitors the resources, and updates VCS with the resource status. An agent typically brigs resources online, take resources offlineand monitors resources to determine their state.
Q: – How VCS Controls Resources ?
Each resource type has a corresponding agent process that manages all resources of that type.
- Agents have one or more entry points that perform a set of actions on resources.
- Each system runs one agentfor each active resource type
Q: – What are the main functions of LLT,GAB & HAD in veritas cluster ?
Low-Latency Transport(LLT) :-
- Is responsible for sending heartbeat messages
- Transports cluster communication traffic to every active system
- Balances traffic load across multiple network links
- Maintains the communication link state
- Is a nonroutable protocol
- Runs on an Ethernet network
Group Membership Services/Atomic Broadcast (GAB)
- Performs two functions:
– Manages cluster membership; referred to as GAB membership.
– Sends and receives atomic broadcasts of configuration information
- Is a proprietary broadcast protocol
- Uses LLT as its transport mechanism
The High Availability Daemon (HAD)
The VCS engine, the high availability daemon:
– Runs on each system in the cluster
– Maintains configuration and state information for all cluster resources
– Manages all agents
The hashadow daemon monitors HAD.
Q: – What are Failover Policies in Veritas Cluster ?
The FailOverPolicy attribute specifies how a target system is selected:
– Priority: The system with the lowest priority number in the list is selected (default).
– RoundRobin: The system with the least number of active service groups is selected.
– Load: The system with greatest available capacity is selected.
Example configuration: hagrp –modify groupname FailOverPolicy Load
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