Many users familiar with other UNIX variants ask if there is a way to mount a disk image or filesystem contained in a file on a running IRIX system. Such operations are often referred to as "loopback" mounts.
Unfortunately SGI never shipped such a capability in any official release of IRIX. Whether or not it might be possible to add this capability through a user-space driver or utility is a question yet to be answered.
One workaround often suggested is to use a UNIX variant that does support such a mount, and export the resulting filesystem via NFS to the target IRIX system.