HP StorageWorks Device Mapper Multipath Enablement Kit for HP StorageWorks Disk Arrays installation and reference guide Part number: AA-RW8RE-TE First edition: June 2009
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Contents About this guide ................................................................................... 5 Intended audience ...................................................................................................................... Related documentation ................................................................................................................ Document conventions and symbols ...............................................................................................
Tables 1 Document conventions ............................................................................................... 5 2 HP Recommended configuration parameters ............................................................... 13 3 Basic operations of DM Multipath ............................................................................. 20 4 Abbreviations .........................................................................................................
About this guide This guide describes the Device Mapper Multipath enablement for HP StorageWorks Disk Arrays (DM Multipath) and provides information to help you: • • • • Install DM Multipath Configure DM Multipath Use DM Multipath Troubleshoot DM Multipath Intended audience This document is intended for users who install, configure, and manage DM Multipath in their Linux server environment. Readers must be familiar with Linux system administration, including hardware and software installation.
Convention Element • File and directory names • System output Monospace text • Code • Commands, their arguments, and argument values Monospace, italic Monospace, bold text text • Code variables • Command variables Emphasized monospace text IMPORTANT: Provides clarifying information or specific instructions. NOTE: Provides additional information. HP technical support For worldwide technical support information, see the HP support website: http://www.hp.
• http://www.hp.com/go/devicemapper • http://www.hp.com/support/manuals • http://www.hp.com/support/downloads Documentation feedback HP welcomes your feedback. To make comments and suggestions about product documentation, please send a message to storagedocsFeedback@hp.com. All submissions become the property of HP. Product feedback To make comments and suggestions about Device Mapper Multipath Enablement Kit for HP StorageWorks Disk Arrays, please send a message to multipathfeedback@hp.com.
About this guide
1 Introduction This chapter addresses the following topics: • • • • Overview Features Software components DM Multipath operation Overview HPDM Multipath is an enablement kit for HP StorageWorks Disk Arrays based on Device Mapper Multipath, included in the Linux operating system distributions. Device Mapper is an infrastructure in the Linux kernel. It provides a generic way to create virtual layers of block devices. It supports striping, mirroring, snapshots, concatenation, and multipathing.
• Persistent device settings: All the device settings such as load balancing policies, path grouping policies are persistent across reboots and SAN reconfigurations. • Device exclusion: Provides device exclusion feature through blacklisting of devices. • Path monitoring: Periodically monitors each path for status and enables faster failover and failback.
2 Installing HPDM Multipath To install HPDM Multipath tools, complete the following steps: 1. Download the HPDM Multipath tools installation package from the following HP website at: http://www.hp.com/go/devicemapper/ 2. Log in as root to the host system. 3. Copy the installation tar package to a temporary directory (for example, /tmp/HPDMmultipath). 4. Unbundle the package by executing the following commands: # cd /tmp/HPDMmultipath # tar -xvzf HPDMmultipath-.tar.
Installing HPDM Multipath
3 Configuring DM Multipath This chapter addresses the following topics: • Using /etc/multipath.conf File • Setting up Device Mapper Multipath daemon Using /etc/multipath.conf File DM Multipath kit includes a template file with the recommended configuration for HP supported arrays. To configure DM Multipath, edit the /etc/multipath.conf configuration file. This file also enables you to customize DM Multipath for a variety of SAN storage subsystems. The /etc/multipath.
Attribute Description Supported Values “round-robin 0” path_selector Used to select the path selector algorithm to be used for mpath. These algorithms are offered by the kernel mpath target failback Used to manage the time during path group failback prio_callout Executable to obtain a path weight for a block device. Weights are summed for each path group to determine the next path group to be used in case of path failure prio Executable to obtain a path weight for a block device.
# chkconfig --list multipathd 2. Run the following commands to start the Device Mapper Multipath daemons: # chkconfig boot.device-mapper [levels] # chkconfig boot.
Configuring DM Multipath
4 Using DM Multipath This chapter addresses the following topics: • Creating an alias using /etc/multipath.conf file • Clustering Solutions with DM Multipath Creating an alias using /etc/multipath.conf file This section describes various parameters available for updating /etc/multipath.conf file. The multipath devices are created in the /dev/mapper directory in the hosts.
Following is a sample multipath.
vendor product path_grouping_policy getuid_callout path_checker path_selector prio_callout rr_weight failback hardware_handler no_path_retry rr_min_io "HP” "HSV210" group_by_prio "/sbin/scsi_id -g -u -s /block/%n" tur "round-robin 0" "/sbin/mpath_prio_alua /dev/%n" uniform immediate "0" 18 100 } device { ……. …... for targets from other storage controllers } } For example, in a typical configuration, a Linux host with a dual port HBA is connected to an EVA 8000 through two switches.
Paths are grouped based on the path grouping policy. In the previous example, for LUN mpath85, the paths are grouped with the policy as multibus and the devices sdb, sda, sdf, sdi, sdg, sdh, sdac, and sdae belong to the same path group. For the LUN mpath86, the grouping is done with the policy as group_by_prio. The devices sdc, sdk, sdj, and sdt belong to one path group, and the devices sdr, sdu, sdv, and sdw belong to a different path group.
3. Use the DM Multipath device to create the logical volumes that are used by Serviceguard for Linux. Please refer the HP ServiceGuard Compatibility matrix for the supported Operating Systems and the Arrays. NOTE: DM Multipath devices can be used with HP Serviceguard A.11.18 for Linux . The LVM volume groups must be configured on the DM Multipath devices. In HP Service Guard package configuration, the disk monitor must be configured using the DM Multipath device in the format /dev/dm-x.
Using DM Multipath
5 Removing HPDM Multipath tools This chapter addresses the following topic: • Removing HPDM Multipath tools Removing HPDM Multipath tools You can remove HPDM Multipath tools by using the INSTALL shell script. To remove HPDM Multipath tools from your system, complete the following steps: 1. Log in to the system as a root user. 2. From the directory containing the script INSTALL, execute the # ./INSTALL command. 3. Follow the on-screen instructions.
Removing HPDM Multipath tools
6 Troubleshooting Following are the troubleshooting steps for issues that you may encounter while using DM Multipath: • Enter the following commands whenever a new LUN is added or deleted at the Linux host, to update the multipath maps in the kernel: 1. /etc/init.d/multipathd restart 2. multipath -v • If SELinux is enabled, device maps cannot be created and SELinux denies access requested by / sbin/multipathd. NOTE: In some cases, labelling problems can cause SELinux denials.
Troubleshooting
7 Abbreviations Table 4 lists the abbreviations or terms used in this document.
Abbreviations
