HPE StoreEver LTO 5 User manual

HPE StoreEver LTO-5 and LTO-6 Failover
User Guide
Part Number: 5200-2563
Published: December 2017
Edition: 8

Contents
Overview.................................................................................................. 6
Traditional library control path and drive connections without failover..........................................7
Basic path failover.........................................................................................................................9
Basic data path port failover details................................................................................... 9
Basic control path failover details.....................................................................................10
Technology for basic control path failover........................................................................ 11
Advanced path failover............................................................................................................... 12
Driver operation during device open................................................................................ 13
Driver operation while opening a connection to a library control path .............................13
Driver operation during normal communications..............................................................14
Path failure detection....................................................................................................... 14
Path failure recovery........................................................................................................ 14
Active and passive control path drives.............................................................................14
Library controller path failure recovery.............................................................................15
Enabling basic path failover................................................................ 16
Preparing the switches and hosts for failover............................................................................. 16
Hardware-specific requirements for basic failover...................................................................... 17
Hardware-specific requirements for advanced path failover.......................................................17
Installing advanced path failover........................................................ 18
Preparing the SAN...................................................................................................................... 18
Minimize host access....................................................................................................... 18
Configure redundant connections.................................................................................... 18
Review the SAN design guidelines.................................................................................. 18
Preparing the library....................................................................................................................19
Preparing the host.......................................................................................................................19
Configuring failover for the ESL G3 Tape Libraries...........................21
Configuring data path failover..................................................................................................... 21
Library and tape drive prerequisites for basic data path failover......................................21
Library and tape drive prerequisites for advanced data path failover.............................. 21
Library configurations for mixed failover environments....................................................22
Enabling data path failover...............................................................................................22
Verifying data path failover...............................................................................................23
Diagnosing basic data path failover................................................................................. 24
Disabling data path failover..............................................................................................26
Configuring control path failover................................................................................................. 26
Library and tape drive prerequisites for basic control path failover..................................26
Library and tape drive prerequisites for advanced control path failover...........................27
Enabling control path failover for a library partition.......................................................... 27
Configuring the library after enabling control path failure.................................................28
Verifying control path failover........................................................................................... 30
Disabling control path failover.......................................................................................... 30
2Contents

Configuring failover for the MSL3040 or MSL6480 ........................... 32
Control path failover configuration.............................................................................................. 32
Enabling control path failover...........................................................................................32
Locating the library world-wide node name after enabling basic control path failure ......33
Verifying basic control path failover..................................................................................33
Verifying advanced control path failover.......................................................................... 34
Data path failover configuration.................................................................................................. 35
Enabling data path failover...............................................................................................35
Verifying data path failover...............................................................................................36
Configuring failover for other MSL Tape Libraries ........................... 37
Configuring data path port failover..............................................................................................37
Enabling data path port failover....................................................................................... 37
Verifying data path port failover........................................................................................38
Making the standby port be the active port...................................................................... 39
Configuring basic control path failover........................................................................................39
Enabling control path port failover on the library..............................................................39
The “Enable Library Control Path Failover” setting is not selectable............................... 41
Verifying basic control path failover..................................................................................42
Locating the library world-wide node name Configuration requirements after
enabling control path failure ............................................................................................ 42
Configuring the tape drive hosting the library control path..........................................................42
Installing and using Windows advanced path failover drivers.........43
Installing the Windows advanced path failover drivers............................................................... 43
The Windows Installer reports Error 0x80070643............................................................44
Uninstalling the drivers................................................................................................................45
Verifying that the tape and changer drivers are correctly installed............................................. 45
Windows driver theory of operation............................................................................................ 46
Driver components........................................................................................................... 46
Device firmware................................................................................................................51
Installing and using Linux advanced path failover drivers...............52
Installing advanced path failover drivers.....................................................................................52
Updating the driver without rebooting......................................................................................... 53
Device files..................................................................................................................................53
Load balancing options for multiple tape drives..........................................................................53
Common characteristics of both load balancing algorithms.............................................53
Full Balancing algorithm...................................................................................................54
Less Balancing algorithm................................................................................................. 54
Setting the load balancing level....................................................................................... 54
Command line user interface...................................................................................................... 54
Viewing the current driver revision................................................................................... 55
Viewing device status.......................................................................................................55
Setting the preferred path................................................................................................ 56
Rebalancing the paths..................................................................................................... 56
Path rotation exercise function.........................................................................................57
Enabling advanced path failover on a device while the driver is running....................................57
Disabling advanced path failover on a device while the driver is running...................................57
Linux driver theory of operation.................................................................................................. 57
Contents 3

Installing and using HP-UX advanced path failover drivers............. 59
Installing advanced path failover drivers.....................................................................................59
Commands for viewing tape and library devices connected to a system................................... 60
Finding the lockdown path.......................................................................................................... 62
Troubleshooting advanced path failover..................................................................................... 62
Enabling or disabling advanced path failover............................................................................. 62
Troubleshooting failover operation.....................................................64
Locating a failed path..................................................................................................................64
Windows debugging logs and tools............................................................................................ 65
Confirming failover operation........................................................................................... 66
Windows system log.........................................................................................................66
Diagnostic application...................................................................................................... 67
Diagnostic dumps.............................................................................................................73
Linux logs and troubleshooting tools...........................................................................................74
Dumping cached reservation information.........................................................................74
Controlling the level of debug output sent to the console................................................ 74
Reading the trace log....................................................................................................... 75
Library path failover events.........................................................................................................75
Additional tape drive sense codes.............................................................................................. 77
Advanced troubleshooting techniques...............................................79
Preparing to generate Windows driver debug dump log files..................................................... 79
Support and other resources...............................................................81
Accessing Hewlett Packard Enterprise Support......................................................................... 81
Accessing updates......................................................................................................................81
Customer self repair....................................................................................................................82
Remote support.......................................................................................................................... 82
Warranty information...................................................................................................................82
Regulatory information................................................................................................................83
Documentation feedback............................................................................................................ 83
Known issues and workarounds......................................................... 84
Path failover issues are observed on Windows Server 2012......................................................84
Device connectivity is lost after several closely spaced path failovers....................................... 85
The device driver does not connect to the preferred path.......................................................... 85
The device driver does not connect to the highest performance path........................................ 85
A host in a multi-initiator environment does not discover a path to the library controller............ 86
Tape library access commands fail with "Reservation Conflict" errors or "Medium Removal
Prevented" errors........................................................................................................................ 86
Data Protector device discovery with advanced path failover ........ 88
Troubleshooting Commvault Simpana device discovery with HP-
UX 11.31................................................................................................. 90
Commvault Simpana fails to discover devices when run on HP-UX 11.31................................. 90
4Contents

© Copyright 2014, 2016 Hewlett Packard Enterprise Development LP
Acknowledgments
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Enterprise website.

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, Hewlett Packard Enterprise provides High Availability Failover features
for ESL G3 Tape Libraries and the MSL2024, MSL3040, MSL4048, MSL6480, MSL8048, and MSL8096
Tape Libraries with LTO-5 and LTO-6 Fibre Channel tape drives. Failover features are not supported on
the EML and ESL E-Series Tape Libraries.
• High Availability Data Path Failover— Both tape drive 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, the libraries support 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 LTO-6 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.
◦ Available for the MSL2024, MSL4048, MSL6480, MSL8048, MSL8096, and ESL G3 Tape Libraries.
• Advanced failover
◦ Supported on LTO-6 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

◦ Available for the ESL G3, MSL3040, and MSL6480 Tape Libraries.
◦ Not available for the 1/8 G2 Tape Autoloader nor the MSL2024, MSL4048, MSL8048, or MSL8096
Tape Libraries.
Traditional library control path and drive connections
without failover
A typical connection for a Fibre Channel tape library using the drive to bridge commands to the library
controller in a two drive tape library is shown in Figure 1: Typical bridged library controller connection
on page 7.
Figure 1: Typical bridged library controller connection
Traditional library control path and drive connections without failover 7

1. Ultrium Dual Port Fibre Channel Tape Drives
2. Host connection
3. Internal connection
In the typical bridged library controller connection each tape drive has one physical link to the SAN switch
and connects to the SAN switch as one Fibre Channel device.
The tape drive hosting the library controller path connects as one Fibre Channel device containing two
logical units. The tape drive is logical unit number zero and the tape library is logical unit number one.
The tape library Fibre Channel device contains a tape drive logical unit and a media changer logical unit.
The logical view of the tape library is shown in Figure 2: Logical view of traditional configuration on
page 8.
Figure 2: Logical view of traditional configuration
1. Ultrium Dual Port Fibre Channel Tape Drives
2. Lun 0 at the WWPN of this drive
3. Lun 1 at the WWPN of this drive
4. Lun 0 at the WWPN of this drive
5. Host connection
8 Overview

Basic path failover
Basic path failover uses features in the tape drive and library firmware to recover paths following a link
failure.
Basic data path port failover details
Basic data path port failover (see Figure 3: Data path port failover example configuration on page
9) can be configured on each LTO-5 or LTO-6 dual-port Fibre Channel tape drive in the library. When
basic data path port failover is configured, one link is active and is the primary data path. The second link
is a standby data path. The drive verifies that the second link is able to receive a Fibre Channel signal
and completes speed negotiation but the drive does not fully establish a connection using the standby
link. The library user interface might report the standby link as a passive connection.
The drive monitors the links for errors, and following detection of a fault, transfers the fabric identity
(world-wide names) and all settings (mode parameters, encryption settings, etc.) over to the standby link
and then activates that link. When properly configured, the change is minimally disruptive to the host and
does not require any configuration changes on the host or in the backup application.
If no drive commands are outstanding when a failure is detected, the port change happens with virtually
no disruption to the SAN. If a command is outstanding on the link when a failure is detected, the drive is
not able to recover the command so that command fails but the application is able to continue to use the
drive on the new path. Many applications are able to recover from a single command failure as long as
the communication path to the drive is not lost.
Figure 3: Data path port failover example configuration
Basic path failover 9

1. Primary data path
2. Secondary data path
3. Host connection
4. Ultrium dual port Fibre Channel tape drive
Basic control path failover details
Library basic control path port failover (see Figure 4: Control path port failover example configuration
on page 11) is configured with one drive hosting the active logical link to the library controller and a
second drive configured as the passive logical link to the library controller. The library connections share
physical links with the drives while the library has its own identity on the SAN and will appear as a unique
device. Unlike the typical bridged library controller configuration shown in Figure 1: Typical bridged
library controller connection on page 7, basic control path failover uses a Fibre Channel technology
called NPIV, which allows the library to appear on the SAN as a new device with its own worldwide name
instead of appearing as a logical unit behind the tape drive. Connecting as an independent device makes
it possible to change the library controller SAN connection without affecting the drive connection.
If basic data path port failover is also configured, the library control path follows the data path on single
link failures.
With basic control path failover, the ESL G3 library monitors the drive that is hosting the library controller
and the ports on the drive. The library receives notification from the drive of any interface change events
and can quickly detect whether that change indicates a fault. The library also monitors the drive and can
detect when a drive has been removed or otherwise becomes inaccessible. Upon detecting a fault that
would cause loss of communication with the library controller, the library automatically moves the library
control path identity (world-wide names) and all settings (such as reservations and prevent/allow settings)
over to the alternate control path drive and activates the control path on the alternate drive. When
properly configured, the change is minimally disruptive to the host and does not require any configuration
changes on the host or in the backup application.
NOTE:
The MSL libraries monitor drive removal events and if the active control path drive is removed, the
library will automatically move the control path to the standby drive. However, if the control path
drive is not removed but SAN connectively is lost, the administrator might need to use the library
remote management interface to move the control path to the standby drive.
If no library commands are sent while the port is being reconfigured, the port change happens with
virtually no disruption to the SAN. Commands sent while the port is being reconfigured might be
completed but cannot report the command status to the application so the application will receive an
error. Applications that retry commands are able to use the library following reconfiguration of the port.
Applications that do not retry can be restarted remotely without making any hardware configuration
changes.
10 Basic control path failover details

Figure 4: Control path port failover example configuration
1. Primary data path 2. Standby data path
3. Host connection 4. Ultrium Dual Port Fibre Channel Tape Drives
5. Passive logical link to switch shares physical link
on drive #2
6. Active logical link to switch shares physical link
on drive #1
Technology for basic control path failover
Hewlett Packard Enterprise LTO-5 and LTO-6 Fibre Channel tape drives use a technology called N-Port
Identifier Virtualization (NPIV) which is defined as part of the Fibre Channel standards maintained by the
Technology for basic control path failover 11

INCITS/T11 working group (see clause 6) in the FC-LS-2 specification. NPIV allows a single physical port
to connect to a Fibre Channel switch multiple times using multiple node and port names.
Advanced path failover
Advanced path failover uses capabilities in the LTO-6 tape drives and the libraries in which they are
installed, combined with software drivers running on a host system to provide path failover when multiple
paths are available to a tape drive or to a library controller. Advanced path failover is a licensed feature.
An example multi-path configuration is shown in Figure 5: Example multi-path configuration on page
12.
Figure 5: Example multi-path configuration
In this example configuration, two different servers designated as “Server A” and “Server B” each have
two different host interface ports that are connected to two different SANs. Each SAN is connected to the
tape library. The connection between the library and the SAN in this example is a bundle of connections
that contains a connection to one port on each drive in the library. All of the drives in the library have two
ports with one port connected into SAN 1 and the second port connected into SAN 2. The library in this
example has two different drives which are both configured to provide a library control path. Each drive
that is configured to provide a library control path will connect to the SAN as two devices, a tape drive and
a library controller, at two different SCSI logical units.
The list of paths available at one of the servers is shown in the example path list. In this table, the SAN
that contains the path is listed in the first column and the following columns show what device is being
addressed (for example, the SCSI logical unit), the port on the drive that is being accessed, an example
SCSI address, and the worldwide identifier (such as a Fibre Channel worldwide node name) of the
addressed logical unit. The unique portion of the worldwide identifier is highlighted.
Table 1: Example path list
SAN Addressed Logical
Unit
Port Example SCSI
address
Example Logical Unit
Worldwide Identifier
1 Tape drive 1 Port A ID 1 LUN 0 50:01:10:a0:00:00:00:01
1 Library Controller Port A ID 1 LUN 1 50:01:10:a0:00:00:00:02
Table Continued
12 Advanced path failover

SAN Addressed Logical
Unit
Port Example SCSI
address
Example Logical Unit
Worldwide Identifier
2 Tape drive 1 Port B ID 2 LUN 0 50:01:10:a0:00:00:00:01
2 Library Controller Port B ID 2 LUN 1 50:01:10:a0:00:00:00:02
1 Tape drive 2 Port A ID 3 LUN 0 50:01:10:a0:00:00:00:03
1 Library Controller Port A ID 3 LUN 1 50:01:10:a0:00:00:00:02
2 Tape drive 2 Port B ID 4 LUN 0 50:01:10:a0:00:00:00:03
2 Library Controller Port B ID 4 LUN 1 50:01:10:a0:00:00:00:02
In this example the server is able to evaluate the worldwide identifiers to determine that there are two
paths to each of two different tape drives and four paths to a library controller.
In a typical multi-path configuration all of the paths for each device are available to the application which
must resolve redundant paths and choose a preferred path.
When advanced path failover drivers are installed on the server, the drivers will query each device for
support of advanced path failover and if the device supports advanced path failover, the drivers will select
a preferred path for each device and establish a connection using the preferred path. Only one path will
be visible to the application.
Driver operation during device open
When an application requests that a connection to a device be opened, the failover driver will connect to
the selected device, and if that device supports advanced path failover, will negotiate for a connection (a
nexus using INCITS/T10 standards terminology) to that device. Computers running Windows will open a
connection to each device when the server is booted. Computers running HP-UX and Linux don't open a
connection to the device until an application opens the device for reading and/or writing.
Each device supports up to 32 simultaneous failover connections. If a failover connection is available, a
connection between the host driver and the device is created. If no failover connection is available, the
connection that has been idle for the longest time is closed and then the new connection is created. The
server connected to the terminated idle session is notified that the failover connection has been
terminated and the advanced path failover driver on that system will automatically create a new
connection the next time a command is sent to the device.
NOTE:
Systems using advanced path failover should be designed with 32 or fewer active hosts per device
for optimal performance. Hosts should be configured so that they do not send unnecessary polling
commands to the device.
Driver operation while opening a connection to a library control path
In a system configured for advanced path failover at least two tape drives should be configured to provide
a path to the library controller. For additional redundancy, the ESL G3 library allows configuring more than
one standby control path drive. Some library state information is retained in the drive hosting the library
controller so each server that requests a connection to the library controller is required to create a
connection using a path through the same hosting drive. The library controller provides a method for the
administrator to select the preferred control path drive. The advanced path failover driver will query each
Driver operation during device open 13

available control path drive to determine the preferred control path drive (called the ‘active’ control path
drive) before requesting a connection.
Driver operation during normal communications
The advanced path failover driver passes commands through without any command translation and with
minimal additional processing in normal operation to retain the maximum possible performance. During
normal communication the advanced path failover driver does not introduce additional commands that
would cause delays (for example, commands to determine position) during reading and writing.
Path failure detection
The advanced path failover driver uses notifications from the SCSI subsystem that report link failures
immediately following a path failure, which allows recovery to happen as quickly as possible so most
recoveries complete before the standard command timeout. In some operating systems the path failure
notification is received immediately after the failure and the failover drivers are able to perform path failure
recovery even if there are no outstanding commands. In other operating systems the advanced path
failover drivers are only notified of a path failure when a command is transmitted over that path.
Path failure recovery
Following detection of a path failure the advanced path failover driver queries a path verification feature in
the LTO tape drive to test paths until a valid path to the device is detected. The path verification feature
allows rapid detection of failed and valid paths without waiting for long timeouts or hardware-specific
notifications. After a new path has been identified the advanced path failover device driver will send a
command to the device using the new path to notify the device that a path has failed, indicate which
connection has failed, and to provide state information. Upon receipt of a notification that the path has
changed, the target device will automatically transfer all available settings and information from the failed
connection to the new connection and use the state information provided in that change notification to
synchronize the target state with the device driver state then will notify that device driver that it has
successfully synchronized state. Synchronization of the state includes any physical position changes
necessary to position the tape in the correct logical position for that state.
After receiving notification that the state is synchronized between the advanced path failover device driver
and the target device, the advanced path failover device driver can take the steps necessary to recover
any commands that were outstanding at the time of the failure. For most commands recovery is
accomplished by resending the original command.
Notifying the target device of the path change and performing the state synchronization in the target
device removes complex state recovery algorithms from the driver and removes the risk of incorrect tape
positioning during state recovery, resulting in a higher performance, lower complexity, and less risky path
failover method than a traditional driver where all recovery is performed by the driver.
Active and passive control path drives
The SCSI connection to libraries using advanced path failover is through the physical link in a tape drive.
Libraries that support advanced path failover will configure two different tape drives so that they present a
library control path (Medium Changer) device and forward commands addressed to the library control
path device on to the changer controller in the tape library. One of the tape drives will be configured as an
“active” control path drive, which means that the library control device presented by this tape drive will
accept commands such as MOVE MEDIUM for the changer device. One of the tape drives will be
configured as a “passive” control path drive, which means that the library control device presented by this
tape drive will accept device discovery commands such as INQUIRY, but will reject commands such as
MOVE MEDIUM. The advanced path failover drivers will automatically select an “active” path to the library
and will automatically reconfigure which drive is the active control path drive when reconfiguration is
necessary during failover. The tape library user interface will show which control path drive is the current
active control path drive.
14 Driver operation during normal communications

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 15

Enabling basic path failover
To successfully enable basic path failover, complete the following:
Procedure
1. Verify that the switch and host prerequisites are met. See Preparing the switches and hosts for
failover on page 16.
2. Verify that the tape drive and library prerequisites are met and then configure failover for your library:
a. Configuring failover for the ESL G3 Tape Libraries on page 21
b. Configuring failover for the MSL3040 or MSL6480 on page 32
c. Configuring failover for other MSL Tape Libraries on page 37
Preparing the switches and hosts for failover
Prerequisites for using basic data and control path failover:
• The library drive FC ports must be attached to a Fibre Channel SAN that supports NPIV and NPIV
must be enabled. LTO-5 and LTO-6 drives need an 8G connection with the fill word set to arb(ff). With
4G connections, set the fill word to idle.
• The switch is running a supported version of software. For a list of supported software, see the
compatibility matrix on the Backup, Recovery and Archive website: http://www.hpe.com/storage/
daprcompatibility
• The drive port FC topology must be in Fabric mode and the switch side must be set to F-port or Auto
Sense.
• The host Fibre Channel port must have a physical path to both the first port and secondary (passive)
port on the Fibre Channel drive.
• For basic data path failover with port zoning, the host Fibre Channel port and both ports on the drive
need to be within the same zone for failover to work.
• For basic data path failover with World Wide Port Name zoning, the host Fibre Channel World Wide
Port Name and a single first port on the drive need to be in the zone.
• For basic control path failover with port zoning the host Fibre Channel ports and the ports on both the
active and secondary drive chosen for basic control path failover will need to be in the same zone.
• For basic control path failover with World Wide Port Name zoning the host Fibre Channel World Wide
Port Name and basic control path failover World Wide Port Name assigned to the library must be in
the same zone. The Library World Wide Port Name is not the same as the World Wide Port Name of
the drive that is hosting the library.
• Hosts connecting to the library may need to be rebooted if the operating system does not support
dynamic device detection.
• Applications on hosts may need to be reconfigured to recognize the new library world wide name.
16 Enabling basic path failover

Prerequisites for using advanced data and control path failover:
• With LTO-5 and LTO-6 drives with an 8G connection, set the fill word set to arb(ff). With 4G
connections, set the fill word to idle.
• The switch is running a supported version of software. For a list of supported software, see the
compatibility matrix on the Barkup, Recovery and Archive website: http://www.hpe.com/storage/
daprcompatibility
• For advanced data path failover, the host must have a physical path to both the first port and
secondary port on the Fibre Channel drive. For full failover capabilities, the two drive ports should be
connected to different switches and the host Fibre Channel ports should also be connected to the
same two switches.
• All drive ports must be zoned in the respective switches.
Hardware-specific requirements for basic failover
Brocade switches
Most recent firmware versions have NPIV enabled by default but it is configured per port and could have
been disabled. Verify that NPIV is enabled.
For best reliability use firmware revisions v6.2.2f, v6.3.2d, v6.4.3e, v7.1.1c or newer, depending on the
switch family. See the Design Guide for Backup and Archive for current supported revisions on the
Backup, Recovery and Archive website: http://www.hpe.com/storage/daprcompatibility
To enable NPIV on a Brocade switch, navigate to port administration and execute an advance view.
Cisco switches
Some Cisco switches that support NPIV do not have NPIV enabled by default. The Cisco MDS 9148 may
disable NPIV when power cycled.
To enable NPIV on a Cisco switch use Cisco_Device_Manager > Admin > Feature_Control or use the
Cisco CLI commands show NPIV status and NPIV enable.
Hardware-specific requirements for advanced path failover
The NPIV settings are not needed for advanced path failover. For supported switch firmware versions,
see the Design Guide for Backup and Archive on the Backup, Archive and Recovery website at: http://
www.hpe.com/storage/daprcompatibility
B-Series switches
For best reliability use revision v7.1.1c, or newer. LTO-5 and LTO-6 drives work best with 8G connections
configured with arb(ff) type 3, which is done by using the portcfgfillword command to set the ports to use
fill word type 3. The fill word for 4G connections should be set to idle.
C-Series switches
For best reliability use minimum revision 5.2(8)
H-Series switches
For best reliability use minimum revision v7.4.0.21.0.
Hardware-specific requirements for basic failover 17

Installing advanced path failover
To successfully install advanced path failover, complete the following:
Procedure
1. Prepare the SAN. See Preparing the SAN on page 18.
2. Prepare the library. See Preparing the library on page 19.
3. Prepare the host. See Preparing the host on page 19.
Preparing the SAN
To prepare the SAN, review the following:
Procedure
1. Minimize host access on page 18.
2. Configure redundant connections on page 18.
3. Review the SAN design guidelines on page 18.
4. Verify that the switch prerequisites are met. See Preparing the switches and hosts for failover on
page 16.
Minimize host access
Advanced path failover is supported for a maximum of 32 hosts connected to each tape drive or tape
library. Each host should have two to four ports for a total of 64 to 128 connections to each tape drive or
tape library.
Connecting more than 32 hosts may cause performance degradation if extra hosts are attempting to
access the drives or library while another host is using the device.
Use switch zoning or Secure Manager to configure the SAN or library so that only hosts that need to
access the devices are able to connect.
Configure redundant connections
Each tape drive in the library has two ports. For best results the drives should be connected to two
different SANs, with all of the first ports connected to one SAN and all of the second ports connected to
another SAN. The total number of SAN switch ports required for connecting the library is twice the
number of tape drives installed in the library.
If both ports for a tape drive are connected to the same switch, fault tolerance is reduced as a single
switch failure will cause loss of connectivity. If only one switch is available, that switch must be zoned to
create two logical SANs.
Review the SAN design guidelines
The general SAN design guidelines for tape are documented at: http://www.hpe.com/storage/
daprcompatibility
18 Installing advanced path failover

Preparing the library
Advanced path failover is a licensed feature with Control Path Failover and Data Path Failover licensed
separately. Licenses for all failover solutions are also available as a high-availability bundle. Control Path
Failover provides path fault tolerance for the robot controller and Data Path Failover provides fault
tolerance for the tape drive data path. Each feature is licensed once for each tape library and then
enabled separately for every partition and tape drive. The settings may be different for different partitions
and drives depending on the user requirements.
When advanced path failover is enabled for either the control path or the data path, the library partition
and/or tape drives with advanced path failover enabled can only be used by hosts with the advanced path
failover driver installed. If the tape drive or tape library detects that advanced path failover is enabled and
a request to access the media or move media is received from a host that is not using an advanced path
failover driver, the drive or library will reject the command with an additional sense code of 82h/93h,
FAILOVER SESSION SEQUENCE ERROR. That error code should only be reported to an application if
the advanced path failover drivers are not installed on that host.
In a mixed environment where some hosts have advanced path failover drivers installed and some hosts
do not, the library should be partitioned so that one partition is accessed by hosts that are using
advanced path failover and the second partition is accessed by hosts that are not using advanced path
failover. In some cases a mix of host operating systems might be used with a single partition. For example
a Windows host might be running the library control agent and another operating system is performing
backups. In that configuration advanced control path failover could be enabled and the advanced path
failover driver installed on the library control host but the drives may be configured without path failover.
If a single ESL G3 library needs to serve both hosts that have advanced path failover drivers installed and
hosts without advanced path failover drivers, the ESL G3 library can be configured with pools of drives
where all of the hosts with advanced path failover drivers use one pool of drives and advanced data path
failover is enabled on those drives. At the same time, a second pool of drives in the same partition either
has basic data path failover enabled or no data path failover enabled. The second pool of drives is
accessed by the hosts that do not have advanced path failover drivers. Other libraries do not support
mixing basic and advanced path failover, so the drives connected to hosts without advanced path failover
drivers must be configured without path failover enabled.
For instructions on installing advanced path failover for your library, see:
• ESL G3: Configuring failover for the ESL G3 Tape Libraries on page 21
• MSL3040 or MSL6480: Configuring failover for the MSL3040 or MSL6480 on page 32
Preparing the host
Hosts used with advanced path failover must be configured with two different data paths and should be
configured with two different HBAs. For supported HBAs see the compatibility matrix on the Backup,
Recovery and Archive Solutions website:
NOTE:
Always verify that your HBA and HBA driver are supported with path failover. For example, the
Emulux HBA driver that is included in the Red Had distribution must be upgraded.
For the highest level of fault protection, connect two different HBAs in the host to two different SANs. This
configuration provides full fault tolerance from both an HBA failure and a SAN switch failure. If a single
HBA is used, an HBA failure might result in loss of connection.
The advanced path failover driver for Windows selects the first path it discovers. If you want the driver to
select a particular SAN path, configure the host so that the HBA for your preferred path is installed in the
position with the lowest numbered bus location. Refer to your server documentation for bus location
Preparing the library 19

information. The Linux path failover driver and the HP-UX operating system have built-in load balancing
and when a tape drive is opened the operating system selects the best path based on the current path
loading.
The Linux advanced path failover driver has a command for requesting a partition path to be preferred.
That setting will only persist until the next reboot because the hardware configuration can change when
the server reboots. The driver is unable to detect whether the hardware is the same as the previous boot
so the preferred setting is not retained across reboots. You can use a boot time script to set the preferred
path at each boot when the hardware configuration is stable. For persistent path binding, use Linux udev
rules to create persistent paths.
After the host has been configured and booted, install the drivers necessary for the host operating
system.
•Installing and using Windows advanced path failover drivers on page 43
•Installing and using Linux advanced path failover drivers on page 52
•Installing and using HP-UX advanced path failover drivers on page 59
20 Installing advanced path failover