HP StoreEver MSL6480 Tape Library - Manual (Page 8)

Figure 2 Logical view of traditional configuration
1. HP Ultrium Dual Port Fibre Channel Tape Drives
2. Lun 0 at the WWPN of this drive
3. Lun 1 at the WWPN of this drive
4. Lun 0 at the WWPN of this drive
5. Host connection
Basic path failover
Basic path failover uses features in the tape drive and library firmware to recover paths following
a link failure.
Basic data path port failover details
Basic data path port failover (see Figure 3 (page 9) ) can be configured on each LTO-5 or later
generation dual-port Fibre Channel tape drive in the library. When basic data path port failover
is configured, one link is active and is the primary data path. The second link is a standby data
path. The drive verifies that the second link is able to receive a Fibre Channel signal and completes
speed negotiation but the drive does not fully establish a connection using the standby link. The
library user interface might report the standby link as a passive connection.
The drive monitors the links for errors, and following detection of a fault, transfers the fabric identity
(world wide names) and all settings (mode parameters, encryption settings, etc.) over to the standby
link and then activates that link. When properly configured, the change is minimally disruptive to
the host and does not require any configuration changes on the host or in the backup application.
If no drive commands are outstanding when a failure is detected, the port change happens with
virtually no disruption to the SAN. If a command is outstanding on the link when a failure is detected,
the drive is not able to recover the command so that command fails but the application is able to
continue to use the drive on the new path. Many applications are able to recover from a single
command failure as long as the communication path to the drive is not lost.
8 Overview