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: Data path port failover example configuration
on page
9) can be configured on each LTO-5 or LTO-6 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.
Figure 3: Data path port failover example configuration
Basic path failover
9