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 can open a connection to the library controller through another tape drive.
A tape drive hosts the library control path, maintaining 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. When the library state changes, the library notifies
the advanced path failover driver that a state change 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
connects to a different drive and configures the new drive as the preferred control path drive. After
activating a passive control path drive, the path failover driver downloads the state information from the
previous control path drive. The newly activated control path drive notifies the library controller that the
preferred control path drive has changed and then the library disables 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.
Library controller path failure recovery
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