veritas cluster architecture

Veritas Cluster

Cluster Information

Veritas cluster 4.0 can have upto 32 nodes.

LLT (Low-Latency Transport)

veritas uses a high-performance, low-latency protocol for cluster communications. LLT runs directlyon top of the data link provider interface (DLPI) layer ver ethernet and has several major junctions:

sending and receiving heartbeatsmonitoring and transporting network traffic over multiple network links to every active systemwithin the clusterload-balancing traffic over multiple linksmaintaining the state of communicationproviding a nonroutable transport mechanism for cluster communications.

Group membership services/Atomic Broadcast (GAB)

GAB provides the following:

Group Membership Services - GAB manitains the overall cluster membership by the way ofits Group Membership Sevices function. Heartbeats are used to determine if a system is activemember, joining or leaving a cluster. GAB determines what the position of a system is in withina cluster.Atomic Broadcast - Cluster configuration and status information is distributed dynamically toall system within the cluster using GAB's Atomic Broadcast feature. Atomic Broadcast ensuresall active system receive all messages, for every resource and service group in the cluster.Atomic means that all system receive the update, if one fails then the change is rolled back onall systems.

High Availability Daemon (HAD)

The HAD tracks all changes within the cluster configuration and resource status by communicatingwith GAB. Think of HAD as the manager of the resource agents. A companion daemon calledhashadow moniotrs HAD and if HAD fails hashadow attempts to restart it. Like wise if hashadowdaemon dies HAD will restart it. HAD maintains the cluster state information. HAD uses the main.cffile to build the cluster information in memory and is also responsible for updating the configurationin memory.

VCS architecture

So putting the above altogether we get:

Agents monitor resources on each system and provide status to HAD on the local system

Veritas Cluster Architecture http://www.datadisk.co.uk/html_docs/veritas/veritas_cluster.htm

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HAD on each system send status information to GABGAB broadcasts configuration information to all cluster membersLLT transports all cluster communications to all cluster nodesHAD on each node takes corrective action, such as failover, when necessary

Service Groups

There are three types of service groups:

Failover - The service group runs on one system at any one time.Parallel - The service group can run simultaneously pn more than one system at any time.Hybrid - A hybrid service group is a combination of a failover service group and a parallelservice group used in VCS 4.0 replicated data clusters, which are based on Veritas VolumeReplicator.

When a service group appears to be suspended while being brought online you can flush the servicegroup to enable corrective action. Flushing a service group stops VCS from attempting to bringresources online or take them offline and clears any internal wait states.

Resources

Resources are objects that related to hardware and software, VCS controls these resources throughthese actions:

Bringing resource online (starting)Taking resource offline (stopping)Monitoring a resource (probing)

When you link a parent resource to a child resource, the dependency becomes a component of theservice group configuration. You can view the dependencies at the bottom of the main.cf file.

Proxy Resource

A proxy resource allows multiple service groups to monitor the same network interface. This reducesthe network traffic that would result from having multiple NIC resources in different service groupsmonitoring the same interface.

Phantom Resource

The phantom resource is used to report the actual status of a service group that consists of onlypersistent resources. A service group shows an online status only when all of its nonpersistentresources are online. Therefore, if a service group has only persistent resources (network interface),VCS considers the group offline, even if the persistent resources are running properly. By adding aphantom resource, the status of the service group is hsown as online.

scsi-initiator-id

All node within the cluster must have a unique scsi-initiator-id, to set the scsi-initiator-id follow


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below:

At the OBP set the scsi-initiator-id to 61.

OK> setenv scsi-initiator-id 6

OK> printenv scsi-initiator-id

When the server has booted create and enter the following in /kernel/drv/glm.conf2.

name="glm" parent=/pci@1f,4000

unit-address="5"

scsi-initiator-id=6;

To check that the scsi-initiator-id has been set use the following command3.

# prtconf -v # search through the listing finding scsi-initiator-id

Installation

Before you install VCS make sure you have the following perpared:

Cluster NameUnique ID NumberHostnames of the serversDevices names of the network interfaces for the private networksRoot accessAble to perform remote shell from all systems (.rhosts file requires updating)VCS software

To install VCS follow below, remember that both hosts must be able to root rsh into each otherwithoutrequesting for a password: -

Start the VCS installation by entering

# ./installVCS

1.

Enter the cluster name and the unique ID number

Cluster name: cluster1

Unique ID: 1

2.

Enter the systems names that require clustering

System names: sun1 sun2

3.

The software will now check each servers remote access and then install the software on eachserver.

4.

A list will appear detailing all the NIC's available. Select the FIRST then the SECOND privatenetworks links

5.


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First Link: hme0

Second Link: qfe0

Answer Yes to the next questions (Servers are identical)6.The LLT and GAB files will be copied and a successful message will appear7.


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veritas cluster architecture

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