User`s guide
Persistent Binding forTape Devices
To simplify management of servers in SAN-based data-centers, the Sun StorageTek
TM
SAN
Foundation software stack in the Solaris OS dynamically detects devices in a SAN and builds
associated /dev tree entries without requiring you to edit conguration les.
In most cases, this process greatly simplies SAN management. However, for tape devices, you
might like the ability to explicitly specify how that /dev entries are created and to ensure the
/dev entries are identical across multiple servers on a SAN. This chapter describes how you can
specify this tape binding in the Solaris OS while retaining the benets of automatic discovery for
disk-based devices.
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 dierent hosts, the
/dev/rmt link can be dierent on each of these hosts. This dierence 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.
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