REDHAT DEVICE-MAPPER MULTIPATH 4.6 Configuration

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[Page 1] Red Hat DEVICE-MAPPER MULTIPATH 4.6

Using Device-Mapper Multipath Configuration and Administration 4.6 DM_Multipath ISBN: N/A Publication date: July 2008 ...

[Page 2] Red Hat DEVICE-MAPPER MULTIPATH 4.6

This book provides information on using the Device-Mapper Multipath feature of Red Hat Enterprise Linux 4.6 Using Device-Mapper Multipath ...

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Using Device-Mapper Multipath: Configuration and Administration Copyright © 2008 Red Hat, Inc. Copyright © 2008 Red Hat, Inc. This material may only be distributed subject to the terms and conditions set forth in the Open Publication License, V1.0 ...

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Using Device-Mapper Multipath ...

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Preface .................................................................................................................... vii 1. Audience ...................................................................................................... vii 2....

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vi ...

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Preface This book describes the Device Mapper Multipath (DM-Multipath) feature of Red Hat Enterprise Linux. 1. Audience This book is intended to be used by system administrators managing systems running the Linux operating system. It requires familia...

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• Linux Virtual Server Administration — Provides information on configuring high-performance systems and services with the Linux Virtual Server (LVS). • Red Hat Cluster Suite Release Notes — Provides information about the current release of R...

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If you have to run a command as root, the root prompt (#) precedes the command: # gconftool-2 italic Courier font Italic Courier font represents a variable, such as an installation directory: install_dir/bin/ bold font Bold font represents applicatio...

[Page 10] Red Hat DEVICE-MAPPER MULTIPATH 4.6

Warning A warning indicates potential data loss, as may happen when tuning hardware for maximum performance. Preface x ...

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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 cable...

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Figure 1.1. Active/Passive Multipath Configuration with One RAID Device 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 po...

[Page 13] Red Hat DEVICE-MAPPER MULTIPATH 4.6

Figure 1.2. Active/Passive Multipath Configuration with Two RAID Devices As in the example shown in Figure 1.1, “Active/Passive Multipath Configuration with One RAID Device”, there are two I/O paths to each RAID device. With DM-Multipath configur...

[Page 14] Red Hat DEVICE-MAPPER MULTIPATH 4.6

Figure 1.3. Active/Active Multipath Configuration with One RAID Device 2. Storage Array Support By default, DM-Multipath includes support for the most common storage arrays that support DM-Multipath. The supported devices can be found in the multipat...

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Component Description program whenever a block device is added or it can be run by the initramfs file system. multipathd daemon Monitors paths; as paths fail and come back, it may initiate path group switches. Provides for interactive changes to mult...

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6 ...

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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 w...

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multipath device. 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 in the cluster you perform one of the followi...

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filter = [ "r/disk/", "r/sd.*/", "a/.*/" ] Multipath Devices in Logical Volumes 9 ...

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10 ...

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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 ...

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3. Save the configuration file and exit the editor. 4. Execute the following commands: modprobe dm-multipath service multipathd start multipath -v2 The multipath -v2 command prints out multipathed paths that show which devices are multipathed. If the...

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device-mapper ioctl cmd 9 failed: Invalid argument device-mapper ioctl cmd 14 failed: No such device or address create: 3600a0b80001327d80000006d43621677 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:0 sdb 8:...

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[root@rh4cluster1 ~]# multipath -F [root@rh4cluster1 ~]# multipath -v2 create: 3600a0b80001327d80000006d43621677 [size=12 GB][features="0"][hwhandler="0"] \_ round-robin 0 \_ 2:0:0:0 sdb 8:16 \_ 3:0:0:0 sdf 8:80 create: 3600a0b800...

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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 ...

[Page 26] Red Hat DEVICE-MAPPER MULTIPATH 4.6

is specified in the defaults and devices sections of the 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 stora...

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wwid 26353900f02796769 } 2.2. Blacklisting By Device Name You can blacklist device types by device name so that they will not be grouped into a multipath device by specifying a devnode entry in the devnode_blacklist section of the configuration file....

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out, as follows. #defaults { # udev_dir /dev # polling_interval 10 # selector "round-robin 0" # path_grouping_policy multibus # getuid_callout "/sbin/scsi_id -g -u -s /block/%n" # prio_callout /bin/true # path_checker readsector0 ...

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Attribute Description multibus = all valid paths in 1 priority group group_by_serial = 1 priority group per detected serial number group_by_prio = 1 priority group per path priority value group_by_node_name = 1 priority group per target node name The...

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Attribute Description A value of manual specifies that failback can happen only with operator intervention. The default value is manual. no_path_retry A numeric value for this attribute specifies the number of times the system should attempt to use a...

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Attribute Description group_by_serial = 1 priority group per detected serial number group_by_prio = 1 priority group per path priority value group_by_node_name = 1 priority group per target node name path_selector Specifies the default algorithm to u...

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multipaths { multipath { wwid 3600508b4000156d70001200000b0000 alias yellow path_grouping_policy multibus path_checker readsector0 path_selector "round-robin 0" failback manual rr_weight priorities no_path_retry 5 } multipath { wwid 1DEC___...

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no_path_retry and rr_min_io, as described in Table 4.3, “Device Attributes”. If the device is active/passive, but it automatically switches paths with I/O to the passive path, you need to change the checker function to one that does not send IO/ ...

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Attribute Description A numeric value greater than zero specifies deferred failback, expressed in seconds. A value of manual specifies that failback can happen only with operator intervention. features The extra features of multipath devices. The onl...

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# path_checker tur # rr_weight priorities # } #} Configuration File Devices 25 ...

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26 ...

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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 C...

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\_ 2:0:0:6 sdb 8:16 [active][ready] \_ round-robin 0 [prio=1][enabled] \_ 3:0:0:6 sdc 8:64 [active][ready] 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 s...

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Option Description -l Display the current multipath configuration gathered from sysfs and the device mapper. -ll Display the current multipath configuration gathered from sysfs, the device mapper, and all other available components on the system. -f ...

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enter help to get a list of available commands, you can enter a interactive command, or you can enter CTRL-D to quit. The multipathd interactive console can be used to troubleshoot problems you may be having with your system. For example, the followi...

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Index Symbols /etc/multipath.conf package, 11 A active/active configuration definition, 1 illustration, 3 active/passive configuration definition, 1 illustration, 1 alias parameter , 20 configuration file, 7 B bindings_file parameter, 18 blacklist co...

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feedback, viii, viii G getuid_callout parameter, 18, 23 H hardware_handler parameter, 23 K kpartx command , 4 L local disks, ignoring, 12 LVM physical volumes multipath devices, 8 lvm.conf file , 8 M modprobe command, 11 multipath command , 4, 11 opt...