Sun Cluster 3.1 Concepts Guide

Global Namespace

The Sun Cluster software mechanism that enables global devices is the global namespace. The global namespace includes the /dev/global/ hierarchy as well as the volume manager namespaces. The global namespace reflects both multihost disks and local disks (and any other cluster device, such as CD-ROMs and tapes), and provides multiple failover paths to the multihost disks. Each node physically connected to multihost disks provides a path to the storage for any node in the cluster.

Normally, the volume manager namespaces reside in the /dev/md/diskset/dsk (and rdsk) directories, for Solaris Volume Manager; and in the /dev/vx/dsk/disk-group and /dev/vx/rdsk/disk-group directories, for VxVM. These namespaces consist of directories for each Solaris Volume Manager diskset and each VxVM disk group imported throughout the cluster, respectively. Each of these directories houses a device node for each metadevice or volume in that diskset or disk group.

In the SunPlex system, each of the device nodes in the local volume manager namespace is replaced by a symbolic link to a device node in the /global/.devices/node@nodeID file system, where nodeID is an integer that represents the nodes in the cluster. Sun Cluster software continues to present the volume manager devices, as symbolic links, in their standard locations as well. Both the global namespace and standard volume manager namespace are available from any cluster node.

The advantages of the global namespace include:

Local and Global Namespaces Example

The following table shows the mappings between the local and global namespaces for a multihost disk, c0t0d0s0.

Table 3–2 Local and Global Namespaces Mappings


Local Node Namespace 

Global Namespace 

Solaris logical name 



DID name 



Solaris Volume Manager 



VERITAS Volume Manager 



The global namespace is automatically generated on installation and updated with every reconfiguration reboot. You can also generate the global namespace by running the scgdevs(1M) command.