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StoreEver LTO 5
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HP StoreEver LTO-5, StoreEver LTO-6 User Manual

HPE StoreEver LTO-5 and LTO-6 Failover User Guide

Part Number: 5200-2563 Published: December 2017 Edition: 8

Contents

Overview.................................................................................................. 6
Enabling basic path failover................................................................ 16
Traditional library control path and drive connections without failover..........................................7
Basic path failover.........................................................................................................................9
Advanced path failover............................................................................................................... 12
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
Preparing the library....................................................................................................................19
Preparing the host.......................................................................................................................19
Configuring failover for the ESL G3 Tape Libraries...........................21
Configuring data path failover..................................................................................................... 21
Configuring control path failover................................................................................................. 26
2 Contents
Configuring failover for the MSL3040 or MSL6480 ........................... 32
Control path failover configuration.............................................................................................. 32
Data path failover configuration.................................................................................................. 35
Configuring failover for other MSL Tape Libraries ........................... 37
Configuring data path port failover..............................................................................................37
Configuring basic control path failover........................................................................................39
Locating the library world-wide node name Configuration requirements after
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
Uninstalling the drivers................................................................................................................45
Verifying that the tape and changer drivers are correctly installed............................................. 45
Windows driver theory of operation............................................................................................ 46
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
Command line user interface...................................................................................................... 54
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
Linux logs and troubleshooting tools...........................................................................................74
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
4 Contents
©
Copyright 2014, 2016 Hewlett Packard Enterprise Development LP
Acknowledgments
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Notices
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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 driver­based 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
6 Overview
intervention.
◦ 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 on page 7.
Figure 1: Typical bridged library controller connection
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
5. Passive logical link to switch shares physical link on drive #2

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
4. Ultrium Dual Port Fibre Channel Tape Drives
6. Active logical link to switch shares physical link on drive #1
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
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
Port Example SCSI
address
Example Logical Unit Worldwide Identifier
12 Advanced path failover
Table Continued
SAN Addressed Logical
Unit
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.
Port Example SCSI
address
Example Logical Unit Worldwide Identifier

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

Configuring failover for the ESL G3 Tape Libraries

Configuring data path failover

When basic data path failover is enabled, the drive is presented on the first drive Fibre Channel port, by default, and the second Fibre Channel port is a passive port. If the primary port goes down, the library transfers various settings over to the passive port and then enables the failover port. When advanced path failover is enabled, the drive is presented to the host over both SANs and the host driver determines the active path.
For increased fault tolerance, select two drives that have less common library infrastructure for the active and passive control path drives. For example, if you choose drive 1 as the active drive, choose a passive drive in another cluster or library module.

Library and tape drive prerequisites for basic data path failover

• The HPE StoreEver ESL G3 LTO-5/LTO-6 Ultrium Data Path Failover license is installed on the library.
• The host has a physical path to both the primary and secondary ports on the FC drive.
• The tape drive is an LTO-5 or LTO-6 Fibre Channel tape drive.
• The library is attached to a Fibre Channel SAN that supports NPIV.
• The drive port Fibre Channel topology is configured in Fabric mode.
• All paths to the Fibre Channel drive are accessible from the same HBA and all of the devices need to be within the same zone.
• If Secure Manager is enabled, hosts that need access to the control path have robotics device access to the first Fibre Channel port on both the active control path drive and the standby control path drive.

Library and tape drive prerequisites for advanced data path failover

• The HPE StoreEver ESL G3 LTO-5/LTO-6 Ultrium Data Path Failover license is installed on the library.
• The host has a physical path to both the primary and secondary FC drive ports.
• The tape drive is an LTO-6 Fibre Channel tape drives.
• Host drivers are configured on all hosts.
The hosts that do not have advanced path failover drivers will see the drives but will not be able to write, read, or send move commands.
The advanced path failover drivers also support drives configured with basic path failover or without failover configured.
• If necessary, the library is configured for mixed failover environments.
• If Secure Manager is enabled, hosts that need access to the control path have robotics device access to all Fibre Channel ports on both the active control path drive and the standby control path drive.
Configuring failover for the ESL G3 Tape Libraries 21
The host will have two different worldwide names for the two different HBAs and each worldwide name may be granted access to all ports or one name may be granted access to the first Fibre Channel port and the second name may be granted access to the second Fibre Channel port.

Library configurations for mixed failover environments

In a mixed failover environment, hosts with advanced path failover drivers and hosts without advanced path failover drivers all access the same tape library. Only a host using advanced path failover drivers can access a tape drive configured for advanced path failover. The library reports an error if a host without the advanced path failover drivers attempts to access a tape drive configured for advanced path failover.
The ESL G3 supports two methods of configuring the library to operate in mixed failover environments:
• Library partitions—The library is configured in multiple partitions such that all of the hosts accessing all of the tape drives in the partition are either using advanced failover drivers or are not using advanced failover drivers.
• Drive pools—The tape drives in a partition are configured into multiple pools 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.

Enabling data path failover

Procedure
1. Log in to the Management Console as a user with Administrator privileges.
2. Select the Physical managed view.
3. Select Setup > Partitions > Data Path Failover.
4. The Data Path Failover (DPF) dialog appears and displays all LTO-5 and LTO-6 drives. You can filter
the list by partition. Select the drives for which you want to enable failover and the type of failover, and then click OK.
a. To enable advanced path failover (ADPF), select the ADPF or Driver box for the drive.
b. To enable basic path failover (BDPF), select the BDPF box for the drive.
NOTE:
Any drives that belong to an access group and have hosts mapped to the second port are considered to be custom mapped. BDPF cannot be enabled on these drives until the custom mapping is removed.
Advanced Data Path Failover can only be enabled on LTO-6 drives. Basic Data Path Failover can be enabled on both LTO-5 and LTO-6 drives.
See the StoreEver Enterprise Systems Library (ESL) G3 Tape Library User Guide for more information on modifying partitions.
22 Library configurations for mixed failover environments
NOTE:
In the following illustration, with 720H and later firmware versions, the ADPF column is labeled Driver.
5. Wait for the configuration change to complete.

Verifying data path failover

To verify that basic data path failover is configured, navigate to Monitor > Drives to launch the Drive Status dialog.
When basic data path failover is enabled for a drive:
Procedure
1. The Link Status for one of the ports is listed as Active.
2. The Link Status for the second drive is listed as Passive, meaning that this is the failover port.
3. The Data Path Failover column displays Enabled.
When advanced data path failover is enabled for a drive:
• The Link Status for both ports is listed as Active.
• The Data Path Failover column displays Enabled.
Verifying data path failover 23
• To verify that basic or advanced data path failover is working:
• From the Fibre Channel switch's management console, down the main Fibre Channel port to a drive.
• From the host computers confirm that the drive is still accessible. After confirming that the drive is still accessible the host logs should show a failover event.
• To verify that failover occurred, navigate to Monitor > Drives to launch the Drive Status dialog. The link status for the first port is Down, and the link status for the second port is Active as shown below.

Diagnosing basic data path failover

When a drive failover occurs, the Drives subsystem has a Warning state, which is displayed in the
Overall System Status section of the Management Console.
24 Diagnosing basic data path failover
Configuring failover for the ESL G3 Tape Libraries 25
Click Drives to display the Event List, and then select the event and click Details to see more information about the failover event. The Repair tab provides detailed instructions on how to troubleshoot and fix the problem.

Disabling data path failover

Procedure
1. Log in to the Management Console as a user with Administrator privileges.
2. Select the Physical managed view.
3. Select Setup > Partitions > Data Path Failover.
4. Unselect the data path failover box for the drive being configured, and then click OK.
a. To disable ADPF, uncheck the ADPF or Driver box for the drive.
b. To disable BDPF, uncheck the BDPF box for the drive.
5. Wait for the configuration change to complete.
6. Verify the configuration change by selecting Monitor > Drives. Data Path Failover is shown as Disabled.
After advanced path failover is disabled, multiple paths to each device will be presented to the host. The advanced path failover driver supports devices with or without advanced path failover enabled so uninstalling the advanced path failover driver is not required when advanced path failover is disabled.

Configuring control path failover

When basic control path failover (BCPF) is enabled, the library is presented on the first drive Fibre Channel port. If basic data path failover is configured on the drive, the second Fibre Channel port will be one of the control path failover ports.
When advanced control path failover (ACPF) is enabled, the library is presented on all the Fibre Channel ports of all the drives configured to handle the library control path.
For both ACPF and BCPF, configure a secondary control path drive and the ports on that drive will be standby control path failover ports that can be activated in the event of complete loss of connection to the primary control path drive. Standby control path drive ports are still active data path ports and can be used for tape drive access even when the drive is configured as a passive control path drive.
If the active control path port goes down, the library transfers various settings to one of the passive ports and then either the library enables the control path failover port for basic path failover or the driver switches the active path for advanced path failover.

Library and tape drive prerequisites for basic control path failover

Procedure
1. The HPE StoreEver ESL G3 LTO-5/LTO-6 Ultrium Control Path Failover license is installed on the
library.
2. The host has a physical path to both the primary and secondary FC drives.
3. The tape drives that will be active and standby control path drives are LTO-5 or LTO-6 FC tape drives.
4. The library is attached to a Fibre Channel SAN that supports NPIV.
26 Disabling data path failover
5. The drive port Fibre Channel topology is configured in Fabric mode.
6. All paths to the control path Fibre Channel drive are accessible from the same HBA and all of the
devices are within the same zone.
7. If Secure Manager is enabled, hosts that need access to the control path have robotics device access to the first Fibre Channel port on both the active control path drive and the standby control path drive.

Library and tape drive prerequisites for advanced control path failover

Procedure
1. The HPE StoreEver ESL G3 LTO-5/LTO-6 Ultrium Control Path Failover license is installed on the
library.
2. The host has a physical path to both the primary and secondary FC drives.
3. The tape drives that will be active and standby control path drives are LTO-6 FC tape drives.
4. Advanced path failover drivers are installed and configured on all hosts.
The hosts that do not have advanced path failover drivers will see the drives but will not be able to write, read, or send move commands. The advanced path failure drivers also support drives configured with basic path failover or without failover configured.
5. If Secure Manager is enabled, hosts that need access to the control path must be given robotics device access to all Fibre Channel ports on both the active control path drive and the standby control path drive. The host will have two different worldwide names for the two different HBAs and each worldwide name may be granted access to all ports or one name may be granted access to the first Fibre Channel port and the second name may be granted access to the second Fibre Channel port.

Enabling control path failover for a library partition

1. Log on as administrator.
2. From the main console, select Setup > Partitions > Control Path.
3. When prompted, select the partition you would like to configure. Click OK.
The Control Path dialog box appears.
4. In the Control Path (CP) Selection pane, select the primary control path drive.
5. Select the drive you wish to configure as the standby control path failover drive from the Control Path
Failover (CPF) Selection list.
NOTE:
LTO-4 drives do not support failover. LTO-5 and LTO-6 drives support Basic Path Failover, but only LTO-6 drives are supported for advanced path failover.
6. Under CPF Mode, select the control path failover type.
• For basic control path failover, select Basic.
• For advanced control path failover, select Driver or Advanced.
Library and tape drive prerequisites for advanced control path failover 27
NOTE:
With firmware versions 720H and later, the Advanced button shown in this illustration is labeled Driver.
7. Click OK.

Configuring the library after enabling control path failure

Library configuration requirements when using Secure Manager
Use the Secure Manager Configuration Wizard to map hosts that have been granted access to FC drive ports.
Procedure
1. For basic control path failover, map hosts that have been granted access to the control path device to
the first FC drive port.
2. For advanced control path failover, map hosts that have been granted access to the control path device to both FC ports.
28 Configuring the library after enabling control path failure
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