A technique maps the capacity of storage devices, such as disks, into any RAID group of a volume of a storage system regardless of the location of the RAID group within a volume block number (VBN) space of the volume. The technique separates disks and mapped VBN ranges, allowing for flexibility in the description and extension of RAID group capacities, while providing disk addition policies that support location-independent disk insertion into RAID groups. The technique also provides a disk label structure that supports the provision of multiple VBN ranges within a RAID group and within individual disks. Moreover, the technique provides file system support for allocation and topology management of the multiple mapped VBN ranges within disks and RAID groups, as well as noncontiguous VBN ranges across the RAID groups in the volume.