The Oracle Solaris 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 Oracle Solaris host 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 host for each metadevice or volume in that disk set or disk group.
In the Oracle Solaris Cluster software, each device host in the local volume manager namespace is replaced by a symbolic link to a device host in the /global/.devices/node@nodeID file system. nodeID is an integer that represents the nodes in the cluster. Oracle Solaris 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:
Each host remains fairly independent, with little change in the device administration model.
Devices can be selectively made global.
Third-party link generators continue to work.
Given a local device name, an easy mapping is provided to obtain its global name.
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
The global namespace is automatically generated on installation and updated with every reconfiguration reboot. You can also generate the global namespace by using the cldevice command. See the cldevice(1CL) man page.