Planning the Global Devices and Cluster File Systems

This section provides the following guidelines for planning global devices and for planning cluster file systems:

• Guidelines for Highly Available Global Devices and Cluster File Systems

• Mount Information for Cluster File Systems

For more information about global devices and about cluster files systems, see the Sun Cluster 3.1 10/03 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 layout for global devices and for cluster file systems.

• 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 the file systems 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 for cluster file systems in the /global directory, unless you are prohibited by other software products. By using the /global directory, you can more easily distinguish cluster file systems, which are globally available, from local file systems.

• The following VxFS features are not supported in a Sun Cluster 3.1 configuration.

  • Quick I/O

  • Snapshots

  • Storage checkpoints

  • VxFS-specific mount options:

    • convosync (Convert O_SYNC)

    • mincache

    • qlog, delaylog, tmplog

  • VERITAS CFS requires VERITAS cluster feature & VCS

  Cache advisories can be used, but the effect is observed on the given node only.

  All other VxFS features and options that are supported in a cluster configuration are supported by Sun Cluster 3.1 software. See VxFS documentation for details about VxFS options that are supported in a cluster configuration.

• VxFS mount requirement – Globally mount and unmount a VxFS file system from the primary node. The primary node is the node that masters the disk on which the VxFS file system resides. This method ensures that the mount or unmount 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 that is mounted on /global/a and another file system that is mounted on /global/a/b. To ignore this rule can cause availability and node boot-order problems. These problems would occur 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. An example is different slices on the same disk.