HP StoreEver MSL6480 Tape Library - Manual (Page 14)

tape library user interface will show which control path drive is the current active control path
drive.
Library controller path failure recovery
In most cases the library controller path failure recovery is the same as the tape drive path failure
recovery. If all paths to the drive hosting the library controller have failed, the advanced path
failover driver is capable of opening a connection to the library controller through another tape
drive.
The library control path is hosted by a tape drive, which maintains some state information on behalf
of the library controller. The state information maintained by the tape drive includes reservations,
media removal restrictions, and may contain special mode settings. Any time that the library state
changes, the library notifies the advanced path failover driver that a state change has occurred
and then the advanced path failover driver retrieves a cache of the state information.
When all paths to the drive that was hosting the library control path fail, the advanced path failover
driver will connect to a different drive and configure the new drive as the preferred control path
drive. After activating a passive control path drive the path failover driver will download the state
information from the previous control path drive. The newly activated control path drive will notify
the library controller that the preferred control path drive has changed and the library will disable
the previous control path drive. Any servers still connected to the original control path drive are
notified that the preferred control path drive has changed and the advanced path failover driver
on those servers will automatically change the preferred path for future commands to the new
preferred control path drive.
14 Overview