Planning the Global Devices and Cluster File Systems

This section provides guidelines for planning global devices and cluster file systems. For more information about global devices and cluster files systems, see the Sun Cluster 3.1 Concepts Guide.

Guidelines for Highly Available Global Devices and Cluster File Systems

Sun Cluster software 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. You do not need to use software mirroring if the storage device provides hardware RAID as well as redundant paths to disks.

• Disks – When you mirror, lay out file systems 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.

Mount Information for Cluster File Systems

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 the /global directory enables you to easily distinguish cluster file systems, which are globally available, from local file systems.

• VxFS mount requirement – Globally mount and unmount a VxFS file system from the primary node (the node that masters the disk on which the VxFS file system resides) to ensure that the operation succeeds. A VxFS file system mount or unmount operation that is performed from a secondary node might fail.

• 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).