Manual

Figure 3 Data path port failover example configuration
1. Primary data path
2. Secondary data path
3. Host connection
4. HP Ultrium dual port Fibre Channel tape drive
Basic control path failover details
Library basic control path port failover (see Figure 4 (page 10)) may be configured with one drive
hosting the active logical link to the library controller and a second drive configured as the passive
logical link to the library controller. The library connections share physical links with the drives but
the library has its own identity on the SAN and will show up as a unique device. Unlike the typical
bridged library controller configuration shown in “Typical bridged library controller connection”
(page 7), basic control path failover uses a Fibre Channel technology called NPIV, which allows
the library to show up on the SAN as a new device with its own worldwide name instead of
showing up as a logical unit behind the tape drive. Connecting as an independent device makes
it possible to change the library controller SAN connection without affecting the drive connection.
If basic data path port failover is also configured, the library control path follows the data path
on single link failures.
With basic control path failover, the ESL G3 library monitors the drive that is hosting the library
controller and the ports on the drive. The library receives notification from the drive of any interface
change events and can quickly detect whether that change indicates a fault. The library also
monitors the drive and can detect when a drive has been removed or otherwise becomes
inaccessible. Upon detecting a fault that would cause loss of communication with the library
controller, the library automatically moves the library control path identity (world wide names) and
all settings (such as reservations and prevent/allow settings) over to the alternate control path drive
and activates the control path on the alternate drive. 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.
Basic path failover 9