Related Manuals for Red Hat ENTERPRISE LINUX 5.1 DM MULTIPATH
Summary of Contents for Red Hat ENTERPRISE LINUX 5.1 DM MULTIPATH
- Page 1 Red Hat Enterprise Linux 5.1 DM Multipath Device-Mapper Multipath Configuration and Administration...
- Page 2 All other trademarks referenced herein are the property of their respective owners. The GPG fingerprint of the security@redhat.com key is: CA 20 86 86 2B D6 9D FC 65 F6 EC C4 21 91 80 CD DB 42 A6 0E...
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Page 3: Table Of Contents
Preface 1. Audience ........................v 2. Related Documentation ....................v 3. Feedback ........................v 4. Document Conventions ....................vi 4.1. Typographic Conventions ..................vi 4.2. Pull-quote Conventions ..................viii 4.3. Notes and Warnings ................... viii 1. Device Mapper Multipathing 1.1. Overview of DM-Multipath ..................... 1 1.2. -
Page 5: Preface
3. Feedback If you spot a typo, or if you have thought of a way to make this manual better, we would love to hear from you. Please submit a report in Bugzilla (http://bugzilla.redhat.com/bugzilla/) against the component rh-cs. Be sure to mention the manual's identifier:... -
Page 6: Document Conventions
Preface rh-MPIO(EN)-5.1 (2008-07-31T15:20) By mentioning this manual's identifier, we know exactly which version of the guide you have. If you have a suggestion for improving the documentation, try to be as specific as possible. If you have found an error, please include the section number and some of the surrounding text so we can find it easily. - Page 7 Typographic Conventions Proportional Bold This denotes words or phrases encountered on a system, including application names; dialogue box text; labelled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example: Choose System > Preferences > Mouse from the main menu bar to launch Mouse Preferences.
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Page 8: Pull-Quote Conventions
Preface a server-pool. Under Apache HTTP Server 2.0, the responsibility for creating and maintaining these server-pools has been abstracted to a group of modules called Multi-Processing Modules (MPMs). Unlike other modules, only one module from the MPM group can be loaded by the Apache HTTP Server. 4.2. - Page 9 Notes and Warnings Important Important boxes detail things that are easily missed: configuration changes that only apply to the current session, or services that need restarting before an update will apply. Ignoring Important boxes won't cause data loss but may cause irritation and frustration.
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Page 11: Device Mapper Multipathing
Chapter 1. Device Mapper Multipathing Device Mapper Multipathing (DM-Multipath) allows you to configure multiple I/O paths between server nodes and storage arrays into a single device. These I/O paths are physical SAN connections that can include separate cables, switches, and controllers. Multipathing aggregates the I/O paths, creating a new device that consists of the aggregated paths. - Page 12 Chapter 1. Device Mapper Multipathing • HBA failure • FC cable failure • SAN switch failure • Array controller port failure With DM-Multipath configured, a failure at any of these points will cause DM-Multipath to switch to the alternate I/O path. Figure 1.2, “Active/Passive Multipath Configuration with Two RAID Devices”...
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Page 13: Storage Array Support
Storage Array Support In this configuration, I/O can be spread among those four paths. Figure 1.3. Active/Active Multipath Configuration with One RAID Device 1.2. Storage Array Support By default, DM-Multipath includes support for the most common storage arrays that support DM- Multipath. -
Page 14: Dm-Multipath Setup Overview
Chapter 1. Device Mapper Multipathing Component Description kpartx command Creates device mapper devices for the partitions on a device It is necessary to use this command for DOS-based partitions with DM- MP. The kpartx is provided in its own package, but the device- mapper-multipath package depends on it. -
Page 15: Multipath Devices
Chapter 2. Multipath Devices Without DM-Multipath, each path from a server node to a storage controller is treated by the system as a separate device, even when the I/O path connects the same server node to the same storage controller. DM-Multipath provides a way of organizing the I/O paths logically, by creating a single multipath device on top of the underlying devices. -
Page 16: Multipath Device Attributes
Chapter 2. Multipath Devices a cluster. For information on the multipaths section of the multipath configuration file, see see Section 4.4, “Multipaths Device Configuration Attributes”. • If you want the system-defined user-friendly names to be consistent across all nodes in the cluster, set up all of the multipath devices on one machine. -
Page 17: Setting Up Dm-Multipath
Chapter 3. Setting Up DM-Multipath This chapter provides step-by-step example procedures for configuring DM-Multipath. It includes the following procedures: • Basic DM-Multipath setup • Ignoring local disks • Adding more devices to the configuration file 3.1. Setting Up DM-Multipath Before setting up DM-Multipath on your system, ensure that your system has been updated and includes the device-mapper-multipath package. -
Page 18: Ignoring Local Disks When Generating Multipath Devices
Chapter 3. Setting Up DM-Multipath service multipathd start multipath -v2 The multipath -v2 command prints out multipathed paths that show which devices are multipathed. If the command does not print anything out, ensure that all SAN connections are set up properly and the system is multipathed. Section 5.1, “Multipath For further information on the multipath command output, see Command... - Page 19 Ignoring Local Disks when Generating Multipath Devices [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:1 sdc 8:32 \_ 3:0:0:1 sdg 8:96 create: 3600a0b80001327d800000070436216b3 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:2 sdd 8:48 \_ 3:0:0:2 sdh 8:112 create: 3600a0b80001327510000009b4362163e [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:3 sde 8:64 \_ 3:0:0:3 sdi...
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Page 20: Adding Devices To The Multipathing Database
Chapter 3. Setting Up DM-Multipath create: 3600a0b80001327510000009a436215ec [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:1 sdc 8:32 \_ 3:0:0:1 sdg 8:96 create: 3600a0b80001327d800000070436216b3 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:2 sdd 8:48 \_ 3:0:0:2 sdh 8:112 create: 3600a0b80001327510000009b4362163e [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:3 sde 8:64 \_ 3:0:0:3 sdi... -
Page 21: The Dm-Multipath Configuration File
Chapter 4. The DM-Multipath Configuration File By default, DM-Multipath provides configuration values for the most common uses of multipathing. In addition, DM-Multipath includes support for the most common storage arrays that support DM- Multipath. The default configuration values and the supported devices can be found in the /usr/ share/doc/device-mapper-multipath-0.4.7/multipath.conf.defaults file. -
Page 22: Configuration File Blacklist
Chapter 4. The DM-Multipath Configuration File devices Settings for the individual storage controllers. These values overwrite what is specified in the defaults section of the configuration file. If you are using a storage array that is not supported by default, you may need to create a devices subsection for your array. When the system determines the attributes of a multipath device, first it checks the multipath settings, then the per devices settings, then the multipath system defaults. -
Page 23: Blacklisting By Device Type
Blacklisting By Device Type The following example shows the lines in the configuration file that would blacklist all SCSI devices, since it blacklists are sd* devices. blacklist { devnode "^sd[a-z]" You can use a devnode entry in the blacklist section of the configuraion file to specify individual devices to blacklist rather than all devices of specific type;... -
Page 24: Configuration File Defaults
Chapter 4. The DM-Multipath Configuration File blacklist_exceptions { device { vendor "IBM" product "S/390.*" When specifying devices in the blacklist_exceptions section of the configuration file, you must specify the exceptions in the same way they were specified in the blacklist. For example, a WWID exception will not apply to devices specified by a devnode blacklist entry, even if the blacklisted device is associated with that WWID. - Page 25 Configuration File Defaults defaults { user_friendly_names path_grouping_policy multibus Table 4.1, “Multipath Configuration Defaults” describes the attributes that are set in the defaults section of the multipath.conf configuration file. These values are used by DM-Multipath unless they are overwritten by the attributes specified in the devices and multipaths sections of the multipath.conf file.
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Page 26: Multipaths Device Configuration Attributes
Chapter 4. The DM-Multipath Configuration File Attribute Description If set to uniform, all path weights are equal. The default value is uniform. Specifies path group failback. failback A value of 0 or immediate specifies that as soon as there is a path group whith a higher priority than the current path group the system switches to that path group. - Page 27 Multipaths Device Configuration Attributes Attribute Description Specifies the default algorithm to use in determining what path to path_selector use for the next I/O operation. Specifies path group failback. failback A value of 0 or immediate specifies that as soon as there is a path group whith a higher priority than the current path group the system switches to that path group.
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Page 28: Configuration File Devices
Chapter 4. The DM-Multipath Configuration File wwid 1DEC_____321816758474 alias rr_weight priorities 4.5. Configuration File Devices Table 4.3, “Device Attributes” shows the attributes that you can set for each individual storage device in the devices section of the multipath.conf configuration file. These attributes are used by DM- Multipath unless they are overwritten by the attributes specified in the multipaths section of the multipath.conf file for paths that contain the device. - Page 29 Configuration File Devices Attribute Description Specifies the product name of the storage device to which the product device attributes apply, for example HSV110 (C)COMPAQ. Specifies a regular expression used to blacklist devices by product_blacklist product. Specifies the default path grouping policy to apply to unspecified path_grouping_policy multipaths.
- Page 30 Chapter 4. The DM-Multipath Configuration File Attribute Description which means that all the paths in a path group will always have the same priority. If set to uniform, all path weights are equal. The default value is uniform. A numeric value for this attribute specifies the number of times no_path_retry the system should attempt to use a failed path before disabling queueing.
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Page 31: Dm-Multipath Administration And Troubleshooting
Chapter 5. DM-Multipath Administration and Troubleshooting This chapter will provide information on administering DM-Multipath on a running system. It includes sections on the following topics: • Multipath Command Output • Multipath Queries with multipath Command • Multipath Command Options • Multipath Queries with dmsetup Command •... -
Page 32: Multipath Queries With Multipath Command
Chapter 5. DM-Multipath Administration and Troubleshooting If the path is up and ready for I/O, the status of the path is ready or active. If the path is down, the status is faulty or failed. The path status is updated periodically by the multipathd daemon based on the polling interval defined in the /etc/multipath.conf file. -
Page 33: Determining Device Mapper Entries With The Dmsetup Command
Determining Device Mapper Entries with the dmsetup Command Option Description Remove all multipath devices. Table 5.1. Useful multipath Command Options 5.4. Determining Device Mapper Entries with the dmsetup Command You can use the dmsetup command to find out which device mapper entries match the multipathed devices. - Page 34 Chapter 5. DM-Multipath Administration and Troubleshooting The following command sequence ensures that multipath has picked up any changes to the multipath.conf, # multipathd -k > > reconfigure > > CTRL-D Use the following command sequence to ensure that the path checker is working properly. # multipathd -k >...
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Page 35: Revision_History
Appendix A. Revision_History Revision History Revision 5.1.0 Wed Feb 07 2007 Michael HideoSmithmhideo@redhat.com Resolves: #223810 Fix complete. English only... -
Page 37: Index
Index vendor parameter, 18 wwid parameter, 16 configuring DM-Multipath, 7 Symbols /etc/multipath.conf package, 7 defaults section multipath.conf file, 14 active/active configuration dev/mapper directory, 5 definition, 1 dev/mpath directory, 5 illustration, 2 device name, 5 active/passive configuration device-mapper-multipath package, 7 definition, 1 devices illustration, 1 adding, 10, 18... - Page 38 Index LVM physical volumes adding, 10, 18 multipath devices, 6 lvm.conf file , 6 udev_dir parameter, 15 user_friendly_names parameter , 5, 14, 15 modprobe command, 7 multipath command , 3, 7 options, 22 vendor parameter, 18 output, 21 queries, 22 multipath devices, 5 World Wide Identifier (WWID), 5 logical volumes, 6...
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