Sun Cluster Concepts Guide for Solaris OS

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 that is physically connected to multihost disks provides a path to the storage for any node in the cluster.

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

In the Sun Cluster system, each device node 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 the following:

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 Namespace Mappings

Component or Path 

Local Node Namespace 

Global Namespace 

Solaris logical name 



DID name 



Solaris Volume Manager 



SPARC: 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.