File systems

Ordinarily, you organize a set of files as a file system for convenience and speed in managing data.

In the PowerHA® SystemMirror® system, a shared file system is a journaled file system that resides entirely in a shared logical volume.

You want to plan shared file systems to be placed on external disks that are shared by cluster nodes. Data resides in file systems on these external shared disks in order to be made highly available.

The order in which file systems are mounted is usually not important. However, if this is important to your cluster, you need to plan for some things:

• File systems that exist within a single resource group are mounted in alphanumeric order when the resource group comes online. They are also unmounted in reverse alphanumeric order when the resource group is taken offline.
• If you have shared, nested file systems, additional care is needed. If you have shared, nested file systems within a single resource group, then you must set the filesystems recovery method for the resource group to sequential to guarantee the correct mount order.
• If you have nested file systems that reside in different resource groups, you must additionally plan a parent-child relationship for those resource groups to guarantee the correct mount order.