From the SGI FAQ
The media daemon (mediad(1M)) recognizes the Zip drive. Provided that mediad and the Objectserver have been configured on (they are on by default but can be chkconfig'd off), mediad recognizes the Zip drive at boot time and places it on the desktop as an icon. The icon reflects presence of a disk in the drive. The icon backdrop reflects the type of filesystem on the disk: an envelope for an EFS filesystem and an apple for an HFS filesystem. Mediad automatically mounts formatted disks as the filesystem /zip. You can eject the disk by selecting the icon and using the desktop root menu.
The IRIX 6.2 Disk Manager tool recognizes the Zip drive. You use the Disk Manager to check disk capacity and to format the disk when necessary.
Caution! The Iomega architecture for a read-only disk (such as the "Iomega Tools" disk distributed with the drive) is entirely software-managed. There is no external tab or hole to mark a disk as read-only, and no hardware protection. The media daemon correctly mounts a read-only disk to /zip with 755 permissions. However, it is possible to write to a nominally read-only disk as root; and it is possible to format a read-only disk manually with fx, mkfs, or mkfp.