Methods and apparatus for expanded capacity virtual volumes in a virtualized storage system. A storage controller of the storage system parses a SCSI command block as it is received to generate a tag value indicating a segment of a virtual volume to which the command block is directed. The tag value is used to select one of a plurality of mapping segment objects stored in a memory of the controller. Each mapping segment objects maps logical block addresses of a corresponding segment of a corresponding virtual volume to physical storage addresses on the physical storage devices that comprise the virtual volume. An I/O processing circuit of the controller then processes the SCSI command block in accordance with the mapping information in the selected mapping segment object. In one exemplary embodiment, each segment of a virtual volume comprises 2 terabytes of storage capacity of the virtual volume.