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Daftar IsiAbstract This book provides information on using the Device-Mapper Multipath feature of Red Hat Enterprise Linux 6. This book describes the Device Mapper Multipath (DM-Multipath) feature of Red Hat Enterprise Linux for the Red Hat Enterprise Linux 6 release. This book is intended to be used by system administrators managing systems running the Linux operating system. It requires familiarity with Red Hat Enterprise Linux. For more information about using Red Hat Enterprise Linux, refer to the following resources: Installation Guide - Documents relevant information regarding the installation of Red Hat Enterprise Linux 6. Deployment Guide - Documents relevant information regarding the deployment, configuration and administration of Red Hat Enterprise Linux 6. Storage Administration Guide - Provides instructions on how to effectively manage storage devices and file systems on Red Hat Enterprise Linux 6.
For more information about Red Hat Cluster Suite for Red Hat Enterprise Linux 6, refer to the following resources: High Availability Add-On Overview - Provides a high-level overview of the Red Hat High Availability Add-On. Cluster Administration - Provides information about installing, configuring and managing the High Availability Add-On. Logical Volume Manager Administration - Provides a description of the Logical Volume Manager (LVM), including information on running LVM in a clustered environment. Global File System 2: Configuration and Administration - Provides information about installing, configuring, and maintaining Red Hat GFS2 (Red Hat Global File System 2). Load Balancer Administration - Provides information on configuring high-performance systems and services with the Load Balancer Add-On, a set of integrated software components that provide Linux Virtual Servers (LVS) for balancing IP load across a set of real servers. Release Notes - Provides information about the current release of Red Hat products.
If you find a typographical error in this manual, 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/ against the product Red Hat Enterprise Linux 6 and the component doc-DM_Multipath. When submitting a bug report, be sure to mention the manual's identifier: rh-DM_Multipath(EN)-6 (2013-2-15T15:15) If you have a suggestion for improving the documentation, try to be as specific as possible when describing it. If you have found an error, please include the section number and some of the surrounding text so we can find it easily. This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information. In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts set. The Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not, alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes the Liberation Fonts set by default. 4.1. Typographic ConventionsFour typographic conventions are used to call attention to specific words and phrases. These conventions, and the circumstances they apply to, are as follows. Mono-spaced Bold
Used to highlight system input, including shell commands, file names and paths. Also used to highlight keys and key combinations. For example: To see the contents of the file my_next_bestselling_novel in your current working directory, enter the cat my_next_bestselling_novel command at the shell prompt and press Enter to execute the command.
The above includes a file name, a shell command and a key, all presented in mono-spaced bold and all distinguishable thanks to context. Key combinations can be distinguished from an individual key by the plus sign that connects each part of a key combination. For example: Press Enter to execute the command. Press Ctrl+Alt+F2 to switch to a virtual terminal.
The first example highlights a particular key to press. The second example highlights a key combination: a set of three keys pressed simultaneously. If source code is discussed, class names, methods, functions, variable names and returned values mentioned within a paragraph will be presented as above, in mono-spaced bold. For example: File-related classes include filesystem for file systems, file for files, and dir for directories. Each class has its own associated set of permissions.
Proportional Bold This denotes words or phrases encountered on a system, including application names; dialog box text; labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example: Choose ⤍ ⤍ from the main menu bar to launch Mouse Preferences. In the Buttons tab, click the Left-handed mouse check box and click Close to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand). To insert a special character into a gedit file, choose ⤍ ⤍ from the main menu bar. Next, choose ⤍ from the Character Map menu bar, type the name of the character in the Search field and click Next. The character you sought will be highlighted in the Character Table. Double-click this highlighted character to place it in the Text to copy field and then click the Copy button. Now switch back to your document and choose ⤍ from the gedit menu bar.
The above text includes application names; system-wide menu names and items; application-specific menu names; and buttons and text found within a GUI interface, all presented in proportional bold and all distinguishable by context. Mono-spaced Bold ItalicProportional Bold Italic
Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. For example: To connect to a remote machine using ssh, type ssh username@domain.name at a shell prompt. If the remote machine is example.com and your username on that machine is john, type ssh [email protected]. The mount -o remount file-system command remounts the named file system. For example, to remount the /home file system, the command is mount -o remount /home. To see the version of a currently installed package, use the rpm -q package command. It will return a result as follows: package-version-release
Note the words in bold italics above - username, domain.name, file-system, package, version and release. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system. Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. For example: Publican is a DocBook publishing system.
4.2. Pull-quote ConventionsTerminal output and source code listings are set off visually from the surrounding text. Output sent to a terminal is set in mono-spaced roman and presented thus: books Desktop documentation drafts mss photos stuff svnbooks_tests Desktop1 downloads images notes scripts svgs Source-code listings are also set in mono-spaced roman but add syntax highlighting as follows: package org.jboss.book.jca.ex1;import javax.naming.InitialContext;public class ExClient{ public static void main(String args[]) throws Exception { InitialContext iniCtx = new InitialContext(); Object ref = iniCtx.lookup("EchoBean"); EchoHome home = (EchoHome) ref; Echo echo = home.create(); System.out.println("Created Echo"); System.out.println("Echo.echo('Hello') = " + echo.echo("Hello")); }}Finally, we use three visual styles to draw attention to information that might otherwise be overlooked. Notes are tips, shortcuts or alternative approaches to the task at hand. Ignoring a note should have no negative consequences, but you might miss out on a trick that makes your life easier. 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 a box labeled 'Important' will not cause data loss but may cause irritation and frustration. Warnings should not be ignored. Ignoring warnings will most likely cause data loss. Chapter 1. Device Mapper MultipathingDevice 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. This chapter provides a summary of the features of DM-Multipath that are new for the initial release of Red Hat Enterprise Linux 6. Following that, this chapter provides a high-level overview of DM Multipath and its components, as well as an overview of DM-Multipath setup. 1.1. New and Changed FeaturesThis section lists new and changed features of DM-Multipath that are included with the initial and subsequent releases of Red Hat Enterprise Linux 6. 1.1.1. New and Changed Features for Red Hat Enterprise Linux 6.0Red Hat Enterprise Linux 6.0 includes the following documentation and feature updates and changes. For the Red Hat Enterprise Linux 6 release, the initial DM-Multipath setup procedure for a basic failover configuration has changed. You can now create the DM-Multipath configuration file and enable DM-Multipath with the mpathconf configuration utility, which can also load the device-mapper-multipath module, start the multipathd daemon, and set chkconfig to start the daemon automatically on reboot. The Red Hat Enterprise Linux 6 release provides a new mode for setting up multipath devices, which you set with the find_multipaths configuration file parameter. In previous releases of Red Hat Enterprise Linux, multipath always tried to create a multipath device for every path that was not explicitly blacklisted. In Red Hat Enterprise Linux 6, however, if the find_multipaths configuration parameter is set to yes, then multipath will create a device only if one of three conditions are met: There are at least two non-blacklisted paths with the same WWID. The user manually forces the device creation, by specifying a device with the multipath command. A path has the same WWID as a multipath device that was previously created (even if that multipath device does not currently exist). For instructions on the procedure to follow if you have previously created multipath devices when the find_multipaths parameter was not set, see Section 4.2, "Configuration File Blacklist".
This feature should allow most users to have multipath automatically choose the correct paths to make into multipath devices, without having to edit the blacklist. The Red Hat Enterprise Linux 6 release provides two new path selector algorithms which determine which path to use for the next I/O operation: queue-length and service-time. The queue-length algorithm looks at the amount of outstanding I/O to the paths to determine which path to use next. The service-time algorithm looks at the amount of outstanding I/O and the relative throughput of the paths to determine which path to use next. For more information on the path selector parameters in the configuration file, see Chapter 4, The DM-Multipath Configuration File. In the Red Hat Enterprise Linux 6 release, priority functions are no longer callout programs. Instead they are dynamic shared objects like the path checker functions. The prio_callout parameter has been replaced by the prio parameter. For descriptions of the supported prio functions, see Chapter 4, The DM-Multipath Configuration File. In the Red Hat Enterprise Linux 6 release, the location of the multipath bindings file is /etc/multipath/bindings. The Red Hat Enterprise Linux 6 release provides three new defaults parameters in the multipath.conf file: checker_timeout, fast_io_fail_tmo, and dev_loss_tmo. For information on these parameters, see Chapter 4, The DM-Multipath Configuration File. When the user_friendly_names option in the multipath configuration file is set to yes, the name of a multipath device is of the form mpathn. For the Red Hat Enterprise Linux 6 release, n is an alphabetic character, so that the name of a multipath device might be mpatha or mpathb. In previous releases, n was an integer.
1.1.2. New and Changed Features for Red Hat Enterprise Linux 6.1Red Hat Enterprise Linux 6.1 includes the following documentation and feature updates and changes. 1.1.3. New and Changed Features for Red Hat Enterprise Linux 6.2Red Hat Enterprise Linux 6.2 includes the following documentation and feature updates and changes. The Red Hat Enterprise Linux 6.2 release provides a new multipath.conf parameter, rr_min_io_rq, in the defaults, devices, and multipaths sections of the multipath.conf file. The rr_min_io parameter no longer has an effect in Red Hat Enterprise Linux 6.2. For information on the rr_min_io_rq parameter, see Chapter 4, The DM-Multipath Configuration File. The dev_loss_tmo configuration file parameter can now be set to infinity, which sets the actual sysfs variable to 2147483647 seconds, or 68 years. For information on this parameter, see Chapter 4, The DM-Multipath Configuration File.
1.1.4. New and Changed Features for Red Hat Enterprise Linux 6.3Red Hat Enterprise Linux 6.3 includes the following documentation and feature updates and changes. The default value of the queue_without_daemon configuration file parameter is now set to no by default. The default value of the max_fds configuration file parameter is now set to max by default. The user_friendly_names configuration file parameter is now configurable in the defaults, multipaths, and devices sections of the multipath.conf configuration file. The defaults section of the multipath.conf configuration file supports a new hwtable_regex_match parameter.
1.1.5. New and Changed Features for Red Hat Enterprise Linux 6.4Red Hat Enterprise Linux 6.4 includes the following documentation and feature updates and changes. The defaults section and the devices section of the multipath.conf configuration file support a new retain_attached_hardware_handler parameter and a new detect_prio parameter. For information on the configuration file parameters, see Chapter 4, The DM-Multipath Configuration File.
1.2. Overview of DM-MultipathDM-Multipath can be used to provide: Redundancy DM-Multipath can provide failover in an active/passive configuration. In an active/passive configuration, only half the paths are used at any time for I/O. If any element of an I/O path (the cable, switch, or controller) fails, DM-Multipath switches to an alternate path. Improved Performance DM-Multipath can be configured in active/active mode, where I/O is spread over the paths in a round-robin fashion. In some configurations, DM-Multipath can detect loading on the I/O paths and dynamically re-balance the load.
In this configuration, there is one I/O path that goes through hba1, SAN1, and controller 1 and a second I/O path that goes through hba2, SAN2, and controller2. There are many points of possible failure in this configuration: With DM-Multipath configured, a failure at any of these points will cause DM-Multipath to switch to the alternate I/O path. hba1 to controller1 hba1 to controller2 hba2 to controller1 hba2 to controller2
In this configuration, I/O can be spread among those four paths. 1.3. Storage Array SupportBy default, DM-Multipath includes support for the most common storage arrays that support DM-Multipath. The supported devices can be found in the multipath.conf.defaults file. If your storage array supports DM-Multipath and is not configured by default in this file, you may need to add them to the DM-Multipath configuration file, multipath.conf. For information on the DM-Multipath configuration file, see Chapter 4, The DM-Multipath Configuration File. Some storage arrays require special handling of I/O errors and path switching. These require separate hardware handler kernel modules. 1.4. DM-Multipath ComponentsTable 1.1. DM-Multipath Components | Component | Description |
|---|
dm_multipath kernel module | Reroutes I/O and supports failover for paths and path groups. | mpathconf utility | Configures and enables device mapper multipathing. | multipath command | Lists and configures multipath devices. Normally started up with /etc/rc.sysinit, it can also be started up by a udev program whenever a block device is added. | multipathd daemon | Monitors paths; as paths fail and come back, it may initiate path group switches. Provides for interactive changes to multipath devices. This must be restarted for any changes to the /etc/multipath.conf file. | 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. |
1.5. DM-Multipath Setup OverviewDM-Multipath includes compiled-in default settings that are suitable for common multipath configurations. Setting up DM-multipath is often a simple procedure. The basic procedure for configuring your system with DM-Multipath is as follows: Install the device-mapper-multipath rpm. Create the configuration file and enable multipathing with the mpathconf command. You can also start the multipath daemon with this command if you do not need to edit the configuration file. If necessary, edit the multipath.conf configuration file to modify default values and save the updated file. Start the multipath daemon.
Chapter 2. Multipath DevicesWithout 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. 2.1. Multipath Device IdentifiersEach multipath device has a World Wide Identifier (WWID), which is guaranteed to be globally unique and unchanging. By default, the name of a multipath device is set to its WWID. Alternately, you can set the user_friendly_names option in the multipath configuration file, which sets the alias to a node-unique name of the form mpathn. For example, a node with two HBAs attached to a storage controller with two ports via a single unzoned FC switch sees four devices: /dev/sda, /dev/sdb, dev/sdc, and /dev/sdd. DM-Multipath creates a single device with a unique WWID that reroutes I/O to those four underlying devices according to the multipath configuration. When the user_friendly_names configuration option is set to yes, the name of the multipath device is set to mpathn. When new devices are brought under the control of DM-Multipath, the new devices may be seen in two different places under the /dev directory: /dev/mapper/mpathn and /dev/dm-n. The devices in /dev/mapper are created early in the boot process. Use these devices to access the multipathed devices, for example when creating logical volumes. Any devices of the form /dev/dm-n are for internal use only and should never be used.
You can also set the name of a multipath device to a name of your choosing by using the alias option in the multipaths section of the multipath configuration file. For information on the multipaths section of the multipath configuration file, see Section 4.4, "Multipaths Device Configuration Attributes". 2.2. Consistent Multipath Device Names in a ClusterWhen the user_friendly_names configuration option is set to yes, the name of the multipath device is unique to a node, but it is not guaranteed to be the same on all nodes using the multipath device. Similarly, if you set the alias option for a device in the multipaths section of the multipath.conf configuration file, the name is not automatically consistent across all nodes in the cluster. This should not cause any difficulties if you use LVM to create logical devices from the multipath device, but if you require that your multipath device names be consistent in every node it is recommended that you not set the user_friendly_names option to yes and that you not configure aliases for the devices. By default, if you do not set user_friendly_names to yes or configure an alias for a device, a device name will be the WWID for the device, which is always the same. If you want the system-defined user-friendly names to be consistent across all nodes in the cluster, however, you can follow this procedure: Set up all of the multipath devices on one machine. Disable all of your multipath devices on your other machines by running the following commands: # service multipathd stop# multipath -F Copy the /etc/multipath/bindings file from the first machine to all the other machines in the cluster. Re-enable the multipathd daemon on all the other machines in the cluster by running the following command: # service mutipathd start
If you add a new device, you will need to repeat this process. Similarly, if you configure an alias for a device that you would like to be consistent across the nodes in the cluster, you should ensure that the /etc/multipath.conf file is the same for each node in the cluster by following the same procedure: Configure the aliases for the multipath devices in the in the multipath.conf file on one machine. Disable all of your multipath devices on your other machines by running the following commands: # service multipathd stop# multipath -F Copy the /etc/multipath.conf file from the first machine to all the other machines in the cluster. Re-enable the multipathd daemon on all the other machines in the cluster by running the following command: # service mutipathd start
When you add a new device you will need to repeat this process. 2.3. Multipath Device AttributesIn addition to the user_friendly_names and alias options, a multipath device has numerous attributes. You can modify these attributes for a specific multipath device by creating an entry for that device in the multipaths section of the multipath configuration file. For information on the multipaths section of the multipath configuration file, see Section 4.4, "Multipaths Device Configuration Attributes". 2.4. Multipath Devices in Logical VolumesAfter creating multipath devices, you can use the multipath device names just as you would use a physical device name when creating an LVM physical volume. For example, if /dev/mapper/mpatha is the name of a multipath device, the following command will mark /dev/mapper/mpatha as a physical volume. pvcreate /dev/mapper/mpatha You can use the resulting LVM physical device when you create an LVM volume group just as you would use any other LVM physical device. If you attempt to create an LVM physical volume on a whole device on which you have configured partitions, the pvcreate command will fail. Note that the Anaconda and Kickstart installation programs create empty partition tables if you do not specify otherwise for every block device. If you wish to use the whole device rather than a partition, you must remove the existing partitions from the device. You can remove existing partitions with the kpartx -d and the fdisk commands. If your system has block devices that are greater that 2Tb, you can use the parted command to remove partitions. When you create an LVM logical volume that uses active/passive multipath arrays as the underlying physical devices, you should include filters in the lvm.conf to exclude the disks that underlie the multipath devices. This is because if the array automatically changes the active path to the passive path when it receives I/O, multipath will failover and failback whenever LVM scans the passive path if these devices are not filtered. For active/passive arrays that require a command to make the passive path active, LVM prints a warning message when this occurs. To filter all SCSI devices in the LVM configuration file (lvm.conf), include the following filter in the devices section of the file. filter = [ "r/block/", "r/disk/", "r/sd.*/", "a/.*/" ] Chapter 3. Setting Up DM-MultipathThis chapter provides step-by-step example procedures for configuring DM-Multipath. It includes the following procedures: 3.1. Setting Up DM-MultipathBefore setting up DM-Multipath on your system, ensure that your system has been updated and includes the device-mapper-multipath package. You set up multipath with the mpathconf utility, which creates the multipath configuration file /etc/multipath.conf. If the /etc/multipath.conf file already exists, the mpathconf utility will edit it. If the /etc/multipath.conf file does not exist, the mpathconf utility will use the /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf file as the starting file. If the /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf file does not exist the mpathconf utility will create the /etc/multipath.conf file from scratch.
If you do not need to edit the /etc/multipath.conf file, you can set up DM-Multipath for a basic failover configuration by running the following command. This command enables the multipath configuration file and starts the multipathd daemon. # mpathconf --enable --with_multipathd y If you need to edit the /etc/multipath.conf file before starting the multipathd daemon. use the following procedure to set up DM-Multipath for a basic failover configuration. Run the mpathconf command with the --enable option specified: # mpathconf --enable For information on additional options to the mpathconf command you may require, see the mpathconf man page or run the mpathconf command with the --help option specified. # mpathconf --helpusage: /sbin/mpathconf <command>Commands:Enable: --enable Disable: --disableSet user_friendly_names (Default n): --user_friendly_names <y|n>Set find_multipaths (Default n): --find_multipaths <y|n> Load the dm-multipath modules on enable (Default y): --with_module <y|n>start/stop/reload multipathd (Default n): --with_multipathd <y|n>chkconfig on/off multipathd (Default y): --with_chkconfig <y|n> Edit the /etc/multipath.conf file if necessary. The default settings for DM-Multipath are compiled in to the system and do not need to be explicitly set in the /etc/multipath.conf file. The default value of path_grouping_policy is set to failover, so in this example you do not need to edit the /etc/multipath.conf file. For information on changing the values in the configuration file to something other than the defaults, see Chapter 4, The DM-Multipath Configuration File. The initial defaults section of the configuration file configures your system so that the names of the multipath devices are of the form mpathn; without this setting, the names of the multipath devices would be aliased to the WWID of the device. Save the configuration file and exit the editor, if necessary. Execute the following command: # service multipathd start
Since the value of user_friendly_name is set to yes in the configuration file, the multipath devices will be created as /dev/mapper/mpathn. For information on setting the name of the device to an alias of your choosing, see Chapter 4, The DM-Multipath Configuration File. If you do not want to use user friendly names, you can run the following command: # mpathconf --enable --user_friendly_names n If you find that you need to edit the multipath configuration file after you have started the multipath daemon, you must execute the service multipathd reload command for the changes to take effect. 3.2. Ignoring Local Disks when Generating Multipath DevicesSome machines have local SCSI cards for their internal disks. DM-Multipath is not recommended for these devices. If you set the find_multipaths configuration parameter to yes, you should not have to blacklist these devices. For information on the find_multipaths configuration parameter, see Section 4.3, "Configuration File Defaults". If you do not set the find_multipaths configuration parameter to yes, can use the following procedure to modify the multipath configuration file to ignore the local disks when configuring multipath. Determine which disks are the internal disks and mark them as the ones to blacklist. In this example, /dev/sda is the internal disk. Note that as originally configured in the default multipath configuration file, executing the multipath -v2 shows the local disk, /dev/sda, in the multipath map. # multipath -v2create: SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1 undef WINSYS,SF2372size=33 GB features="0" hwhandler="0" wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 0:0:0:0 sda 8:0 [--------- device-mapper ioctl cmd 9 failed: Invalid argumentdevice-mapper ioctl cmd 14 failed: No such device or addresscreate: 3600a0b80001327d80000006d43621677 undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:0 sdb 8:16 undef ready running `- 3:0:0:0 sdf 8:80 undef ready runningcreate: 3600a0b80001327510000009a436215ec undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:1 sdc 8:32 undef ready running `- 3:0:0:1 sdg 8:96 undef ready runningcreate: 3600a0b80001327d800000070436216b3 undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:2 sdd 8:48 undef ready running `- 3:0:0:2 sdg 8:112 undef ready runningcreate: 3600a0b80001327510000009b4362163e undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:3 sdd 8:64 undef ready running `- 3:0:0:3 sdg 8:128 undef ready running In order to prevent the device mapper from mapping /dev/sda in its multipath maps, edit the blacklist section of the /etc/multipath.conf file to include this device. Although you could blacklist the sda device using a devnode type, that would not be safe procedure since /dev/sda is not guaranteed to be the same on reboot. To blacklist individual devices, you can blacklist using the WWID of that device. Note that in the output to the multipath -v2 command, the WWID of the /dev/sda device is SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1. To blacklist this device, include the following in the /etc/multipath.conf file. blacklist { wwid SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1}After you have updated the /etc/multipath.conf file, you must manually tell the multipathd daemon to reload the file. The following command reloads the updated /etc/multipath.conf file. # service multipathd reload Run the following command to remove the multipath device: # multipath -f SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1 To check that the blacklisted device was not added back, you can run the multipath command, as in the following example. The multipath command defaults to a verbosity level of v2 if you do not specify specify a -v option. # multipathcreate: 3600a0b80001327d80000006d43621677 undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:0 sdb 8:16 undef ready running `- 3:0:0:0 sdf 8:80 undef ready runningcreate: 3600a0b80001327510000009a436215ec undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:1 sdc 8:32 undef ready running `- 3:0:0:1 sdg 8:96 undef ready runningcreate: 3600a0b80001327d800000070436216b3 undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:2 sdd 8:48 undef ready running `- 3:0:0:2 sdg 8:112 undef ready runningcreate: 3600a0b80001327510000009b4362163e undef WINSYS,SF2372size=12G features='0' hwhandler='0' wp=undef`-+- policy='round-robin 0' prio=1 status=undef |- 2:0:0:3 sdd 8:64 undef ready running `- 3:0:0:3 sdg 8:128 undef ready running
3.3. Configuring Storage DevicesBy default, DM-Multipath includes support for the most common storage arrays that support DM-Multipath. The default configuration values, including supported devices, can be found in the multipath.conf.defaults file. If you need to add a storage device that is not supported by default as a known multipath device, edit the /etc/multipath.conf file and insert the appropriate device information. For example, to add information about the HP Open-V series the entry looks like this, where %n is the device name: devices { device { vendor "HP" product "OPEN-V." getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n" }}3.4. Setting Up Multipathing in the initramfs File SystemYou can set up multipathing in the initramfs file system. After configuring multipath, you can rebuild the initramfs file system with the multipath configuration files by executing the dracut command with the following options: # dracut --force --add multipath --include /etc/multipath /etc/multipath If you run multipath from the initramfs file system and you make any changes to the multipath configuration files, you must rebuild the initramfs file system for the changes to take effect. |
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