AllocDisk will assigned a specified amount of space from a logical bucket for the default disk device.

GetDiskFree is used to retrieve the amount of available disk space we have from a logical perspective with the headroom taken out .

GetPathFree will use the path supplied by the caller as the device context for which free space information is returned, this is from a pysical free capacity perspective rather than what the application is allowed to allocated which has to adjust for minimum amount free.

SetDiskLimits is used to set a highwater mark for a device as a minimum free quantity .

DiskAllocated hold information about disk resources consumed on a specific device.