At the most basic level, a folder is a container for BIG-IP configuration objects and files on a BIG-IP device. Virtual servers, pools, and self IP addresses are examples of objects that reside in folders on the system. Folders resemble standard directories, in that the system includes a root folder (represented by the / symbol) that is the parent for other folders on the system.
A folder can contain other folders.
One of the important ways that you can use folders is to set up full or granular synchronization and failover of BIG-IP configuration data in a device group. You can synchronize and fail over all configuration data on a BIG-IP device, or you can synchronize and fail over objects within a specific folder only.
Folders have two specific redundancy attributes that enable granular synchronization and failover of BIG-IP system data within a device group. These two attributes are a device group name and a traffic group name.
This attribute determines the scope of the synchronization, that is, the specific devices to which the system synchronizes the contents of the associated folder. When you create a Sync-Failover device group on a BIG-IP device, the system assigns that device group name as an attribute of folder root. Any other folders that you subsequently create on a device group member then inherit that same device group name, by default.
The result is that when you enable config sync for the local device, the contents of the root folder and any sub-folders are synchronized across the members of the specified device group.
If you want to synchronize a specific sub folder across only a subset of device group members, you can create a second, smaller Sync-Only device group in which the local device is also a member, and then change the sub folder's device group attribute to the new Sync-Only device group name. All objects within that sub folder are then synchronized to the Sync-Only device group, while objects outside of that sub folder are still synchronized to the members of the larger Sync-Failover device group.
This attribute determines the scope of a failover action, that is, the specific configuration objects that will fail over if the device becomes unavailable. If you enabled failover on a device (as part of running the Setup utility or upgrading from a previous BIG-IP version), the device contains the default traffic group named traffic-group-1. The system assigns this traffic group name by default as an attribute of folder root. Any other folders that you subsequently create on a device group member inherit that same traffic group name, by default. The result is that when the local device is a member of a Sync-Failover device group, all failover objects within the root folder and its hierarchy fail over based on the definition of the specified traffic group.
You can assign a different traffic group to a specific sub folder. For example, you can create an iApps application in a sub folder and change the inherited traffic group value of traffic-group-1 to a traffic group that you create, such as traffic-group-2. You can then manually cause traffic-group-2 to fail over to another device so that the iApp application runs on a separate device from traffic-group-1.
At the highest-level, the BIG-IP system includes a root folder. The root folder contains all BIG-IP configuration objects on the system, by way of a hierarchical folder and sub-folder structure within it.
By default, the BIG-IP system assigns a Sync-Failover device group and a traffic group to the root folder. All folders and sub-folders under the root folder inherit these default assignments.