Persistent Binding Overview

The /dev/rmt directory contains links to physical devices under /devices for tape devices. Each tape LUN seen by the system is represented by 24 minor nodes in the form of /dev/rmt/N, /dev/rmt/Nb, and /dev/rmt/Nbn, where N is an integer counter starting from 0. This number is picked by devfsadm during enumeration of new devices. Every new tape logical unit number (LUN) found by devfsadm gets the next available number in /dev/rmt.

Because the /dev/rmt name depends on the order in which devices appear in the device tree, it changes from host to host. For a given tape drive that is seen by two or more different hosts, the /dev/rmt link can be different on each of these hosts. This difference can cause problems for the most common usage of Symantec (VERITAS) NetBackup (SSO option). Also, if the drive is replaced, the links change unless the vendor provides a way to retain the port World-Wide Name (PWWN) of the drive.