Using Multiple Logical Libraries for Library Sharing
Multiple logical libraries are an effective way for the library to simultaneously back
up and restore data from heterogeneous applications. For example, the library can
be partitioned so that it processes:

v Commands from Application A (about Department X) in Logical Library 1

v Commands from Application B (about Department Y) in Logical Library 2

In this configuration, the storage slots and drives in each logical library are

dedicated to that library and are not shared among other libraries. Commands
issued by the applications travel to the library through two unique control paths.
Thus, the data processing for:

v Department X is confined to the storage slots and drives in Logical Library 1

v Department Y is confined to the storage slots and drives in Logical Library 2

Using Multiple Control Paths
In addition to creating multiple logical libraries, any logical library can be
configured to have more than one control path. When configuring additional
control paths, additional library sharing configurations and availability options are
made possible. Access to the logical library is on a first-come, first-served basis and
each control path for a logical library can accept commands while the library is in
use by another control path. By default, only the first drive in a logical library will
be LUN-1 enabled.
For a particular logical library, you can enable as many control paths as there are
drives in that logical library.
Using Multiple Control Paths for Path Failover
Command failures and timeouts are costly. You want your library to run smoothly
and efficiently. To ensure continued processing, the library offers an optional path
failover feature that enables the host device driver to resend the command to an
alternate control path for the same logical library. With control path failover
installed, the alternate control path can include another HBA, SAN, or library
control path drive. The device driver initiates error recovery and continues the
operation on the alternate control path without interrupting the application.
The 2U library does not support Control Path Failover and Data Path Failover. As
a result, there should be no license key entry for ″Path Failover″ on the 2U library.
Path Failover is a combination of two previous features: Control Path Failover (key
entered at the library user interface) and Data Path Failover (key entered at the
device driver interface). The Path Failover feature is available for select LTO 4 tape
drives. Path Failover is not supported for half height drives.
The Path Failover feature can be installed by the customer.

For more information about using the path failover feature, see the Dell PowerVault

TL4000 Failover Configuration Guide, included with the library documentation if

purchased at point of sale and with the customer kit if purchased later.
3-2 Dell PowerVault TL2000 Tape Library and TL4000 Tap e Library User's Guide