Dell TL4000 User Guide - Page 40

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 is 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 that are 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 Multiple control paths In addition to creating multiple logical libraries, any logical library can be configured to have more than one control path. When more control paths are configured, more library sharing configurations and availability options are made possible. Access to the logical library is on a first-come, first-served basis. 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 is LUN-1 enabled. For a particular logical library, you can enable as many control paths as there are drives in that logical library. 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 includes 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. Path failover is a combination of two previous features: control path failover (key that is entered at the library user interface) and data path failover (key that is entered at the device driver interface). For library firmware of 8.xx or lower the path failover feature is available for LTO 4 tape drives.Library firmware levels higher than 8.xx support path failover on LTO 5 drives, and also LTO 4 Full Height drives. Library firmware levels higher than B.50 support path failover on LTO 6 Tape Drives, and also LTO 5 and LTO 4 Full 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 Tape Library User's Guide