This section provides guidelines for planning global devices and cluster file systems. For more information about global devices and cluster files systems, see Sun Cluster 3.0 U1 Concepts.
Sun Cluster does not require any specific disk layout or file system size. Consider the following points when you plan your global device and cluster file system layout.
Mirroring - You must mirror all global devices for the global device to be considered highly available.
Disks - When you mirror, lay out disks so that they are mirrored across disk arrays.
Availability - You must physically connect a global device to more than one node in the cluster for the global device to be considered highly available. A global device with multiple physical connections can tolerate a single-node failure. A global device with only one physical connection is supported, but the global device becomes inaccessible from other nodes if the node with the connection is down.
Consider the following points when you plan mount points for cluster file systems.
Mount point location - Create mount points in the /global directory, unless prohibited by other software products. Using a /global directory enables you to easily distinguish cluster file systems, which are globally available, from local file systems.
Nesting mount points - Normally, you should not nest the mount points for cluster file systems. For example, do not set up one file system mounted on /global/a and another file system mounted on /global/a/b. Ignoring this rule can cause availability and node boot order problems if the parent mount point is not present when the system attempts to mount a child of that file system. The only exception to this rule is if the devices for the two file systems have the same physical node connectivity (for example, different slices on the same disk).