esaProbeScheduleGroupStorageType is a create-time StorageType value describing whether this schedule group's configuration is kept in volatile or non-volatile storage. An administrator relies on it to know whether a shared probe schedule survives a device reboot or must be reconfigured afterward. For example, a schedule group left as volatile storage would disappear on the next reboot, silently reverting all its member probes to running with no group schedule at all.