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Oracle Solaris Cluster Concepts Guide     Oracle Solaris Cluster 4.1
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Document Information


1.  Introduction and Overview

2.  Key Concepts for Hardware Service Providers

3.  Key Concepts for System Administrators and Application Developers

Administrative Interfaces

Cluster Time

Campus Clusters

High-Availability Framework

Global Devices

Device IDs and DID Pseudo Driver

Zone Cluster Membership

Cluster Membership Monitor

Failfast Mechanism

Cluster Configuration Repository (CCR)

Device Groups

Device Group Failover

Device Group Ownership

Global Namespace

Local and Global Namespaces Example

Cluster File Systems

Using Cluster File Systems

HAStoragePlus Resource Type

syncdir Mount Option

Disk Path Monitoring

DPM Overview

Monitoring Disk Paths

Using the cldevice Command to Monitor and Administer Disk Paths

Using the clnode set Command to Manage Disk Path Failure

Quorum and Quorum Devices

About Quorum Vote Counts

About Quorum Configurations

Adhering to Quorum Device Requirements

Adhering to Quorum Device Best Practices

Recommended Quorum Configurations

Quorum in Two-Node Configurations

Quorum in Greater Than Two-Node Configurations

Load Limits

Data Services

Data Service Methods

Failover Data Services

Scalable Data Services

Load-Balancing Policies

Failback Settings

Data Services Fault Monitors

Developing New Data Services

Characteristics of Scalable Services

Data Service API and Data Service Development Library API

Using the Cluster Interconnect for Data Service Traffic

Resources, Resource Groups, and Resource Types

Resource Group Manager (RGM)

Resource and Resource Group States and Settings

Resource and Resource Group Properties

Support for Oracle Solaris Zones

Support for Zones on Cluster Nodes Through Oracle Solaris Cluster HA for Solaris Zones

Criteria for Using Oracle Solaris Cluster HA for Solaris Zones

Requirements for Using Oracle Solaris Cluster HA for Solaris Zones

Additional Information About Oracle Solaris Cluster HA for Solaris Zones

Service Management Facility

System Resource Usage

System Resource Monitoring

Control of CPU

Viewing System Resource Usage

Data Service Project Configuration

Determining Requirements for Project Configuration

Setting Per-Process Virtual Memory Limits

Failover Scenarios

Two-Node Cluster With Two Applications

Two-Node Cluster With Three Applications

Failover of Resource Group Only

Public Network Adapters and IP Network Multipathing

SPARC: Dynamic Reconfiguration Support

SPARC: Dynamic Reconfiguration General Description

SPARC: DR Clustering Considerations for CPU Devices

SPARC: DR Clustering Considerations for Memory

SPARC: DR Clustering Considerations for Disk and Tape Drives

SPARC: DR Clustering Considerations for Quorum Devices

SPARC: DR Clustering Considerations for Cluster Interconnect Interfaces

SPARC: DR Clustering Considerations for Public Network Interfaces


Device Groups

In the Oracle Solaris Cluster software, all multihost devices must be under control of the Oracle Solaris Cluster software. The Oracle Solaris Cluster software automatically creates a raw device group for each disk and tape device in the cluster. However, these cluster device groups remain in an offline state until you access them as global devices.

Note - Device groups are independent of resource groups. One node can master a resource group (representing a group of data service processes). Another node can master the device groups that are being accessed by the data services. However, the best practice is to keep on the same node the device group that stores a particular application's data and the resource group that contains the application's resources (the application daemon). Refer to Relationship Between Resource Groups and Device Groups in Oracle Solaris Cluster Data Services Planning and Administration Guide for more information about the association between device groups and resource groups.

Each cluster node that is physically attached to the multihost disks provides a path to the device group.

Device Group Failover

Because a disk enclosure is connected to more than one cluster node, all device groups in that enclosure are accessible through an alternate path if the node currently mastering the device group fails. The failure of the node that is mastering the device group does not affect access to the device group except for the time it takes to perform the recovery and consistency checks. During this time, all requests are blocked (transparently to the application) until the system makes the device group available.

Figure 3-1 Device Group Before and After Failover

image:This graphic shows a device group before and after a failover.

Device Group Ownership

This section describes device group properties that enable you to balance performance and availability in a multiported disk configuration. Oracle Solaris Cluster software provides two properties that configure a multiported disk configuration: preferenced and numsecondaries. You can control the order in which nodes attempt to assume control if a failover occurs by using the preferenced property. Use the numsecondaries property to set the number of secondary nodes for a device group that you want.

A highly available service is considered down when the primary node fails and when no eligible secondary nodes can be promoted to primary nodes. If service failover occurs and the preferenced property is true, then the nodes follow the order in the node list to select a secondary node. The node list defines the order in which nodes attempt to assume primary control or transition from spare to secondary. You can dynamically change the preference of a device service by using the clsetup command. The preference that is associated with dependent service providers, for example a global file system, is identical to the preference of the device service.

Secondary nodes are check-pointed by the primary node during normal operation. In a multiported disk configuration, checkpointing each secondary node causes cluster performance degradation and memory overhead. Spare node support was implemented to minimize the performance degradation and memory overhead that checkpointing caused. By default, your device group has one primary and one secondary. The remaining available provider nodes become spares. If failover occurs, the secondary becomes primary and the node highest in priority on the node list becomes secondary.

You can set the number of secondary nodes that you want to any integer between one and the number of operational nonprimary provider nodes in the device group.

Note - If you are using Solaris Volume Manager, you must create the device group first, using the metaset command before you use the cldg command to set the property.

The default number of secondaries is 1. The actual number of secondary providers that is maintained by the framework is the number that you want, unless the number of operational nonprimary providers is less than the number that you want. You must alter the numsecondaries property and double-check the node list if you are adding or removing nodes from your configuration. Maintaining the node list and number of secondaries prevents conflict between the configured number of secondaries and the actual number that is allowed by the framework.