HP StoreEver Tape Libraries Failover User Guide (5697-3323, June 2014)

1 Overview
With today’s high dependency on access to business information, safe-guarded data and limited
backup windows, the reliability of the backup hardware and software is vital. Additionally, backup
operations are usually automated, often done at night, and any first pass operator intervention is
done remotely. To assist with these enterprise demands, HP provides High Availability Failover
features for ESL G3 tape libraries and the MSL2024, MSL4048, MSL6480, MSL8048, and
MSL8096 Tape Libraries with LTO-5 and later generation Fibre Channel tape drives. Failover
features are not supported on the HP StoreEver EML and ESL E-Series Tape Libraries.
• High Availability Data Path Failover— Both of the tape drive’s ports are connected to the
SAN. Only one of the ports is used at any one time and the second port is a standby port.
When a link failure on the active port is detected, the second port is used.
• High Availability Control Path Failover — Depending on the library and drive, one or both
ports on the control path drive are configured to present a path to the library controller and
a second drive is configured as a standby library control path drive. The library control path
can be moved to a second link on the drive hosting the control path in the event of a single
path failure and in the event of a complete control path drive connection loss, the standby
library control path drive can be activated and connection to the library control path can be
moved to that drive.
With LTO-5 and LTO-6 tape drives, a driverless path failover feature uses library and drive firmware
to create a new Fibre Channel path to a drive or library if the original path is lost. Most applications
recognize the new path and some will automatically retry commands after the original path is lost.
Other applications may require user intervention to begin using the new path.
With LTO-6 tape drives, in addition to the driverless path failover feature, HP offers a driver-based
path failover feature that uses drivers in conjunction with library and drive firmware to manage
multiple paths across multiple SANs, present a single drive or library path to applications, and
automatically transfer commands to the new path if the original path is lost. This transfer is invisible
to most applications, avoiding the need for user intervention.
These failover features are presented in the library user interface as basic and advanced failover.
• Basic failover
Supported on LTO-5 and later generation FC tape drives. Data path failover requires a
dual-ported drive.
◦
◦ Supported by a combination of tape drive and library firmware features to create a new
Fibre Channel path to a drive or library if the original path is lost.
◦ Most applications recognize the new path and some applications will automatically retry
commands after the original path is lost. Some applications might require user intervention
to begin using the new path.
◦ Is available for the 1/8 G2 Tape Autoloader or MSL2024, MSL4048, MSL6480,
MSL8048, MSL8096, and ESL G3 Tape Libraries.
• Advanced failover
Supported on LTO-6 and later generation FC tape drives.◦
◦ Requires host driver support, in addition to tape drive and library firmware features, to
manage multiple paths across multiple SANs, present a single drive or library path to
applications, and automatically transfer commands to the new path if the original path
is lost.
◦ The transfer to the failover path is invisible to most applications, avoiding the need for
user intervention.
6 Overview