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Sun Cluster 3.0 Concepts

Volume Managers

Sun Cluster uses volume management software to increase the availability of data by using mirrors and hot spare disks, and to handle disk failures and replacements.

Sun Cluster does not have its own internal volume manager component, but relies on the following volume managers:

Volume management software in the cluster provides support for:

When setting up a volume manager in Sun Cluster, you configure multihost disks as Sun Cluster disk devices, a wrapper for a volume manager disk group. The device can be either a Solstice DiskSuite diskset or a VxVM disk group.

You must configure disk groups used for data services for mirroring to make the disks highly available within the cluster.

You can use metadevices or plexes either as a raw device (database application) or to hold UFS file systems.

Volume management objects--metadevices and volumes--come under the control of the cluster, thus becoming disk device groups. For example, in Solstice DiskSuite, when you create a diskset in the cluster (by using the metaset(1M) command), a corresponding disk device group of the same name is created. Then, as you create metadevices in that diskset, they become global devices. Thus, a diskset is a collection of disk devices (DID devices) and hosts to which all devices in the set are ported. All disksets in a cluster need to be created with more than one host in the set to achieve HA. A similar situation occurs when you use VERITAS Volume Manager. The details of setting up each volume manager are included in the appendixes of the Sun Cluster 3.0 Installation Guide.

An important consideration when planning your disksets or disk groups is to understand how their associated disk device groups are associated with the application resources (data) within the cluster. Refer to the Sun Cluster 3.0 Installation Guide and the Sun Cluster 3.0 Data Services Installation and Configuration Guide for discussions of these issues.