Avanti 2.4 removed the emulator's former 8GB disk-size restriction for VMS 6.n guests. Current validation initialized, mounted, wrote, and read a 12GiB image-backed disk on OpenVMS V6.2 using a KZPAA controller.
Avanti presents image-backed and host physical disks to OpenVMS as SCSI block devices, so the applicable OpenVMS, file-system, device-driver, and application limits determine usable capacity. The 12GiB validation does not qualify every controller, patch level, file system, application, or capacity up to the architectural maximum.