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StoreWay Multipathfor LinuxSTOREWAY

User's Guide

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STOREWAY

StoreWay Multipath forLinuxUser's Guide

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The following copyright notice protects this book under Copyright laws which prohibit such actions as, but notlimited to, copying, distributing, modifying, and making derivative works.

Copyright Bull SAS 2011

Printed in France

We acknowledge the rights of the proprietors of the trademarks mentioned in this manual.

All brand names and software and hardware product names are subject to trademark and/or patentprotection.

Quoting of brand and product names is for information purposes only and does not represent trademarkmisuse.

The information in this document is subject to change without notice. Bull will not be liable for errorscontained herein, or for incidental or consequential damages in connection with the use of this material.

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2.1Purpose...................................................................................................................................3

2.2Supported Disk Subsystems........................................................................................................3

2.3Supported Architectures............................................................................................................3

2.4Supported HBA........................................................................................................................4

2.5Packages................................................................................................................................ 4

2.6CD-ROM Contents....................................................................................................................5

3.1Installation and Configuration....................................................................................................73.1.1Automatic Installation..................................................................................................... 73.1.2Manual Installation.........................................................................................................9

3.2Advanced Multipathing Configuration.......................................................................................113.2.1Multipathing over ISCSI configuration.............................................................................11

3.3Multipathing Un-installation......................................................................................................123.3.1Automatic Un-installation...............................................................................................123.3.2Manual Un-installation..................................................................................................12

3.4Multipathing Status Checking: multipath Command..................................................................14

3.5Using Multipath Devices..........................................................................................................15

3.6Using LVM2 on top of the Multipath devices...............................................................................17

3.7Partitions on top of Multipath Devices.......................................................................................20

3.8Boot Support......................................................................................................................... 21

3.9Taking into Account Newly Created Devices..............................................................................23

3.10Checking Path at Boot Time...................................................................................................243.10.1Automatic Checks......................................................................................................24

3.10.2How to Reinitialize Manually the File Paths....................................................................243.10.3How to change multipath policy...................................................................................24

3.11Wiring Subsystems...............................................................................................................25

4.1FC Multipathing errlog............................................................................................................29

4.2Trace example after the first reboot with only a path available.....................................................29

4.3Trace example after a reboot with only a path available.............................................................29

4.4iSCSI Multipath errlog.............................................................................................................30

StoreWay Multipath for Linux - User's Guide i

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ii StoreWay Multipath for Linux - User's Guide

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This document describes how to install and use the product on LinuxOperating System Environment.

Current supported Linux distributions are:

SUSE SLES9 SP3

Red Hat RHEL 4 up2/up4/up5

Red Hat RH 5 up1/up2/up3/up4/up5.

Red Hat RH 6 up1

It is assumed that the reader has a good knowledge of the Linux native I/O concepts andfeatures of Linux kernel 2.6.

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2 StoreWay Multipath for Linux - User's Guide

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The Bull StoreWay Multipath for Linux product provides two complementary features: Scripts to automatically configure and setup the native multipathing failover / load

balancing features of the module of Linux v2.6 kernel.

An additional feature to select the bester path.

This document describes the installation and use of these Linux packages.

The following disk subsystems have been tested and are supported by the Multipathing: subsystems family: and with failover and

loadbalancing mode.

subsystem (only available on RHEL4 up4) with failover mode.

subsystem with failover mode.

and with failover andloadbalancing mode.

The following disk subsystems have been tested and are supported by the Multipathing

feature: subsystem with failover mode.

The following architectures, platforms and distributions are supported:

NovaScale

SLES9 sp3 ia64, RHEL4 up2/up4/up5 ia64, RHEL5 up1/up2/up3/up4/up5.

NovaScale Universal / NovaScale Blade SLES9 sp3 ia32, RHEL4 up2/up4/up5 ia32, RHEL5 up1/up2/up3/up4/up5.

SLES9 sp3 EM-64T, RHEL4 up2/up4/up5 EM-64T,RHEL5 up1/up2/up3/up4/up5 EM-64T.

Novascale F2

RHEL5 up4/up5 ia32, EM-64T.

RHEL6 up1 ia32, EM-64T.


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Emulex HBA / CNA

Qlogic HBA

Brocade HBA / CNA

The multipathing function basic code and modules are directly available on

and Linux distributions.

The on SLES9 or on RHEL4/5package is also included in these distributions and must be installed on your system.

Additional specific packages are needed for SCSI-reservation and will be installed by theinstallation script provided by this product (see the

relevant chapter below).


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The CD-ROM contains the following items. Packages aredelivering the feature and the tool that could gather all the disk-relatedinformation for a better understanding of the SAN configuration. These features aredescribed in the next chapters.

:

sles9

i386

bsan_lib-X.X.X-Y.i586.rpm

scsi_reserve_gui-X.X.X-Y.i586.rpm

bsan_monitor-X.X.X-Y.i586.rpm

ia64

bsan_lib-X.X.X-Y.ia64.rpm

scsi_reserve_gui-X.X.X-Y.ia64.rpm

bsan_monitor-X.X.X-Y.ia64.rpm

x86_64bsan_lib-X.X.X-Y.x86_64.rpm

scsi_reserve_gui-X.X.X-Y.x86_64.rpm

bsan_monitor-X.X.X-Y.x86_64.rpm

rh4/rh5

i386


bsan-X.X.X-Y.i386.rpm

multipath-tools-nec-X.X.X-Y.i386.rpm

ia64

bsan_lib-X.X.X-Y.ia64.rpmbsan-X.X.X-Y.ia64.rpm

multipath-tools-nec-0.4.7-1.ia64.rpm

x86_64

bsan_lib-X.X.X-Y.x86_64.rpm

bsan-X.X.X-Y.x86_64.rpm

multipath-tools-nec-X.X.X-Y.x86_64.rpm

device-mapper-multipath-0.x.x-x.0.BullRH4.x86_64.rpm

rh6

x86_64

multipath-tools-nec-X.X.X-Y.x86_64.rpmbsan_lib-X.X.X-Y.x86_64.rpm

bsan-X.X.X-Y.x86_64.rpm

i386

multipath-tools-nec-X.X.X-Y.i386.rpm


bsan-X.X.X-Y.i386.rpm

(this manual)


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The package (for SLES9)or(for RHEL4/5)must be installed before any installation and configuration.

If you envisage to boot on SAN, consult section 3.8Boot Support before starting thedistribution installation.

An installation script is located on the CD-ROM media, which performs all the installationand configuration actions described below in section 3.1.2 Manual Installation.

On RHEL 6, check the presence of the following package:

To perform the automatic installation, mount the CD-ROM, go to the mounteddirectory and launch the script.

The title and CD-ROM version are displayed on the first line.

The first choice ( ) checks and displays the supporteddistributions, as illustrated below:


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The second choice ( ) installs the packages and configures themultipath. The install is interactive, you must reply to some questions.

Then re-launch the script to continue.


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After the Multipath installation, you can either uninstall Multipath or quit.

The displayed choices are context-dependent.

choice uninstalls all packages.

choice updates the packages (this choice is not displayed in theabove screen).

1. Add the following line in the file on SLES9 or in thefile on RHEL4

options lpfc lpfc_nodev_tmo=5

2. Reload the driver.

3. Enter the following commands:

# modprobe r lpfc

# modprobe lpfc

4. Rebuild the file.


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5. Activate Multipathing feature. According to the distribution:

The Multipathing feature is activated by the following commands:

# /etc/init.d/boot.multipath start

# /etc/init.d/multipathd start

To be directly taken into account at the next reboot, the corresponding service can beactivated by the command:

# insserv boot.multipath multipathd

Also check that the file correctly references the driver in thevariable before issuing the command.

The Multipathing feature is activated by the following commands:

# /etc/rc.d/init.d/multipathd start

To be directly taken into account at the next reboot, the corresponding service can beactivated by the command:

# chkconfig --level 235 multipathd on

# mkinitrd f /boot//initrd kernel

Comment the three lines on the top of the file (as stated in thecomments):

# Blacklist all devices by default. Remove this to enable multipathing

# on the default devices.

# devnode_blacklist {

# devnode "*"

#}

##

6. Reboot the system.

No further configuration should be required for the default options.


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Advanced configuration features are available using the configurationfile, but should be changed only with a good knowledge of their meaning. Default valuesare most often correct, but the following features can be useful:

the ,which defines the frequency of path-health checking the capability to blacklistsome devices for which you dont want the Multipathing

feature to apply.

To support the multipathing over iSCSI you must modify the file andthen reboot or restart the iSCSI service.

Following are the recommended new settings:

node.session.timeo.replacement_timeout = 15

node.conn[0].timeo.noop_out_interval = 5

node.conn[0].timeo.noop_out_timeout = 30


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You can un-install Multipathing either automatically or manually.

To perform the automatic un-installation, do as follows:

1. Mount the CD-ROM,

2. Go to the mounted directory

3. Launch the script. The following screen appears:

4. Select choice 3.

To un-install manually the Multipathing feature (unsuitable), do as follows:

1. Remove the tool:

rpm e bsan_lib-w.x.y-z

rpm e bsan[_monitor]-w.x.y-z


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2. According to the distribution:

Remove the option (options lpfc lpfc_nodev_tmo=5) in thefile.

Run:

mkinitrd

Remove the Multipathing service:

insserv r boot.multipath multipathd

Remove the option (options lpfc lpfc_nodev_tmo=5) infile

Run:mkinitrd f /boot//

Remove the Multipathing service :

chkconfig --level 235 multipathd off


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The command must be used to manage and display the multipathing feature.

# multipath -l

1NEC_iStorage_2000_00000009279003580010A

[size=8 GB][features="0"][hwhandler="0"]

\_ round-robin 0 [active][best]

\_ 2:0:1:1 sde 8:64 [active]

\_ round-robin 0 [enabled]

\_ 3:0:1:1 sdi 8:128 [active]

In this example:

The hexadecimal string (1NEC_iStorage_2000_00000009279003580010A ) isthe unique identification of the device given back by the device-mapper layer. Thisidentification can be used as unique name of devices on the SAN, bringing thecapability of over reconfiguration events.

It also shows the size, the feature and hardware handlers involved, as well as thepriority groups: path are grouped into priority groups where only one priority group isactive for I/O usage. To model an active/active configuration, all paths are includedin the same group. To model an active/passive configuration, the paths which shouldnot be active in parallel are placed in several distinct priority groups. This setting iscompletely automatic at device discovery time.

Both paths on the same priority group are used with round-robin/load balancingalgorithm.

For each path, its physical address (host:bus:target:lun), device node name in /devand major:minor are also displayed.

The current path status (active or not) is also shown.

a) You may change the active priority group with the command.Usage:Example:

switchgroup1NEC_iStorage_2000_00000009279003580010A 1

b) With a subsystem one of the paths is the main one (i.e. the more efficient onefor IOs), the second path is a backup one (see command to display suchinformation). On a failure, the backup path will be activated. After the repair of thefailed path:

with RHEL4 up2, you can use the command to restore the IOs on themain path.

with RHEL4 up4 and upper, it is automatic.


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The corresponding link with the object can be found in thedirectory (on SLES9) or in the directory (on RHEL4).

# cd /dev/disk/by-name

# ll

total 0

drwxr-xr-x 2 root root 320 Jan 5 09:02 .

drwxr-xr-x 5 root root 120 Jan 5 09:02 ..

lrwxrwxrwx 1 root root 10 Jan 5 09:021NEC_iStorage_2000_00000009279003580010A -> ../../dm-2

The device mapper identification can be directly used for file-system or physical volumecreation.

Filesystem creation:

# mke2fs /dev/disk/by-name/1NEC_iStorage_2000_0000009279003580010A

mke2fs 1.36 (05-Feb-2005)

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

1093440 inodes, 2184448 blocks109222 blocks (5.00%) reserved for the super user

First data block=0

67 block groups

32768 blocks per group, 32768 fragments per group

16320 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Writing inode tables: done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.

# mount /dev/disk/by-name/1NEC_iStorage_2000_00000009279003580010A /mnt/workdir

# mount

/dev/sda3 on / type reiserfs (rw,acl,user_xattr)

proc on /proc type proc (rw)

sysfs on /sys type sysfs (rw)

/dev/dm-3 on /mnt/workdir type ext2 (rw)


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# ll /dev/mapper

brw-rw---- 1 root disk 253, 3 Aug 1 11:461NEC_iStorage_2000_0000009279003580010A

crw------- 1 root root 10, 63 Aug 1 18:22 control

# mke2fs /dev/mapper/1NEC_iStorage_2000_0000009279003580010A

mke2fs 1.35 (28-Feb-2004)

Filesystem label=

OS type: Linux



2621440 inodes, 5242880 blocks

262144 blocks (5.00%) reserved for the super user

First data block=0

Maximum filesystem blocks=4294967296

160 block groups




32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,2654208,

4096000



This filesystem will be automatically checked every 39 mounts or180 days, whichever comes first. Use tune2fs -c or -i to override.

# mount /dev/mapper/1NEC_iStorage_2000_0000009279003580010A/mnt/workdir

# mount | grep workdir

/dev/mapper/1NEC_iStorage_2000_0000009279003580010A on /mnt/workdirtype ext3 (rw)


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To make LVM2 recognize the Multipath devices as possible Physical Volumes (PVs), youmust modify the configuration file, such that LVM2 does not scan anduse the physical paths, but only accesses your storage via the Multipathing layer.

To perform that, change the entry in the file as following, and addthe extension types to make LVM2 recognize them:

# types = [ "fd", 16 ]types = [ "device-mapper", 16 ]

# types = [ "fd", 16 ]types = [ "device-mapper", 16 ]

This will allow LVM2 to scan only the paths with SLES9 orwith RHEL4 and reject everything else. (If you are using LVM2 on non-MPIO

devices too, of course you will need to make the necessary adjustments to suit your setup).

Then, you can use and the other LVM2 commands as usual on thepath with SLES9 or path with RHEL4.

Using LVM2, our recommendation is to create Physical Volumes (PVs) on a full disk

(and not on a disk partition).If the lun has been previously used with parted (ex filesystem), it must be fully erasedbefore issuing , with this command:

For :

clean_parts /dev/disk/by-name/lun-name

or, if this command does not exit, with:

dd >/dev/disk/by-name/lun-name /dev/mapper/lun-name

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# pvcreate /dev/disk/by-name/1NEC_iStorage_2000_00000009279003580010A

Physical volume "/dev/disk/by-name/1NEC_iStorage_2000_00000009279003580010A" successfully created

# vgcreate vg001 /dev/disk/by-name/1NEC_iStorage_2000_00000009279003580010A

Volume group "vg001" successfully created

# pvdisplay

--- Physical volume ---

PV Name /dev/dm-2

VG Name vg001

PV Size 8.33 GB / not usable 0

Allocatable yes

PE Size (KByte) 4096

Total PE 2133

Free PE 2133

Allocated PE 0

PV UUID 7m0tyb-k27W-ppxA-upjw-EAUn-PULX-lyiMi0

# lvcreate -L 2G vg001

Logical volume "lvol0" created

# mke2fs /dev/vg001/lvol0

mke2fs 1.36 (05-Feb-2005)

Filesystem label=

OS type: Linux



262144 inodes, 524288 blocks

26214 blocks (5.00%) reserved for the super user

First data block=016 block groups




32768, 98304, 163840, 229376, 294912



This filesystem will be automatically checked every 39 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.


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# mount /dev/vg001/lvol0 /mnt/workdir

# mount

/dev/sda3 on / type reiserfs (rw,acl,user_xattr)

/dev/mapper/vg001-lvol0 on /mnt/workdir type ext2 (rw)

# pvcreate /dev/mapper/1NEC_iStorage_2000_00000009279003580010A

Physical volume "/dev/mapper/1NEC_iStorage_2000_00000009279003580010A" successfully created

# vgcreate vg3 /dev/mapper/1NEC_iStorage_2000_00000009279003580010A

Volume group "vg3" successfully created

# pvdisplay /dev/mapper/1NEC_iStorage_2000_00000009279003580010A

--- Physical volume ---

PV Name /dev/dm-2

VG Name vg3

PV Size 20.00 GB / not usable 0

Allocatable yes

PE Size (KByte) 4096

Total PE 5119

Free PE 5119Allocated PE 0

PV UUID WuXHVw-Yufj-O1UY-kvVx-tAM5-xkoU-nKdi4N

# lvcreate -L 2G vg3

Logical volume "lvol0" created

# mkfs /dev/vg3/lvol0

mke2f1.35 (28-Feb-2004)

Fesystem label=

OSype: Linux

Bck size=4096 (log=2)

Fagmet size=4096 (log=2)

262144nodes, 524288 blocks

26214bocks (5.00%) reserved for the super user

Frt data block=0

Mamum filesystem blocks=536870912

16bock groups

32768bocks per group, 32768 fragments per group

16384nodes per group

Sperbock backups stored on blocks:


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32768, 98304, 163840, 229376, 294912

Wting inode tables: done

Wting superblocks and filesystem accounting information: done

Th filesystem will be automatically checked every 38 mounts or

180day, whichever comes first. Use tune2fs -c or -i to override.

# mount /dev/vg3/lvol0 /mnt/workdir

# mount | grep workdir

/dev/mapper/vg3-vol0 on /mnt/workdir type ext3 (rw)

It is not currently possible to partition the Multipath devices themselves. However, if theunderlaying physical device is partitioned, the Multipath device will reflect those partitionsand the layer will provide /dev/disk/by-name/p1 ... pN deviceswith SLES9 or /dev/mapper/p1pN with RHEL4 so you can access the partitions.

So you will have to partition the devices prior to enabling Multipathing; if you change thepartitioning in the running system, the device-mapper will not automatically detect thischange and reflect the changes. You'll need to reinit it, which in a running system withactive access to the devices will likely imply a reboot.


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Currently, the Multipathing feature is not available neither for the root nor for the bootpartition with SLES9.

The boot support is available only with RHEL4 up4/up5, RHEL5 up1 and withfilesystem and swap on LVs and /boot on a partition (fat with IA64 or ext3 with IA32 andEM64T).The installation phase must be done with . The second path willbe connected when the installation is complete.Then: Mount the StoreWay Multipath for LinuxCD-ROM Run the script and reply to the questions.

Shutdown. Connect the second path. Reboot.

The access path to this boot partition needsto be determined and updated in the file.

[root@tigre3 ~]# bsan

#Copyright (C) by BULL 2003,2006

#cmd: 0.1.2#lib: 2.1.3 all rights reserved.#============== ADP info ======================eth0 == ??? == FW:? V:? == IP@:172.16.101.57 = MAC:00:0e:0c:08:c1:22eth1 == ??? == FW:? V:? == MAC:00:0e:0c:08:c1:23eth2 == ??? == FW:? V:? == MAC:00:0e:0c:72:53:08lo == XER == FW:? V:? == MAC:00:00:00:00:00:00sit0 == XER == FW:? V:? == MAC:00:00:00:00host0 == scsi0 FW:? V:? ==host1 == scsi1 FW:? V:? ==ses0 OK == sg0 , raw? == ESG-SHV SCA HSBP M24 6,0

host2 == scsi2 EMU == FW:1.80A2 (T2D1.80A2) V:8.0.16.27 == DID:030000 =20000000c938c7e1:10000000c938c7e1tgt2.0 == NEC CORPORATION == 2300 == WWN:200000004c7f0445:210000004c7f0445 =

DID:0119efsda OK == sg1 , raw? == NEC iStorage 2000 19900 8,0 0,0 30 R5 008Esdb OK == sg2 , raw? == NEC iStorage 2000 19900 8,16 0,1 30 R5 008F

host3 == scsi3 EMU == FW:3.93A0 (C2D3.93A0) V:8.0.16.27 == DID:030100 =20000000c9272023:10000000c9272023tgt3.0 == XYRATEX == WWN:20000050cc2000b8:24000050cc2000b8 = DID:030d00ses1 OK == sg3 , raw? == XYRATEX F5402E 0,0ses2 OK == sg4 , raw? == XYRATEX F5402E 0,2

tgt3.1 == NEC CORPORATION == 2300 == WWN:200000004c7f0445:230000004c7f0445 =DID:011ce8

sdc OK == sg5 , raw? == NEC iStorage 2000 19900 8,32 1,0 30 R5 008Esdd OK == sg6 , raw? == NEC iStorage 2000 19900 8,48 1,1 30 R5 008F

============== MPIO info ======================dm-1 == 1NEC_____iStorage_2000___00000009279003580008F = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdb == active Ready == failcount 0/dev/sdd == active Ready == failcount 0

dm-0 == 1NEC_____iStorage_2000___00000009279003580008E = 1 pg/2 paths lb

pgrp 0 == 2 paths == active


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/dev/sda == active Ready == failcount 0/dev/sdc == active Ready == failcount 0

============== LVM info =======================VolGroup00 == 19.31 GB = resizable == sdc sdaLogVol01 (dm-6) == 5.88 GB = linear = available = dm-5 = / ext3 (rw)LogVol02 (dm-7) == 3.91 GB = linear = available = dm-5 = /home ext3 (rw)LogVol00 (dm-8) == 1.97 GB = linear = available = dm-5 = swap prio=-1 used=n

To determine the boot partition path enter:

[root@tigre3 hg]# ll /dev/mapper/

total 0

brw-rw---- 1 root disk 253, 0 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008E

brw-rw---- 1 root disk 253, 4 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008E1

brw-rw---- 1 root disk 253, 5 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008E2

brw-rw---- 1 root disk 253, 1 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008F

brw-rw---- 1 root disk 253, 2 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008F1

brw-rw---- 1 root disk 253, 3 Oct 10 2006 1NEC_____iStorage_2000___00000009279003580008F2

crw------- 1 root root 10, 63 Oct 10 2006 control

brw-rw---- 1 root disk 253, 8 Oct 10 2006 VolGroup00-LogVol00



And you can see that the first sda partition is:

1NEC_____iStorage_2000___00000009279003580008E1,

Now modify the/etc/fstab file like this:

/dev/mapper/1NEC_____iStorage_2000___00000009279003580008E1 /boot/efi vfatdefaults 0 0

Then issue the command (/boot on IA32 or EM64T machine).To verify, enter:

[root@tigre3 hg]# df

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/mapper/VolGroup00-LogVol01

6063688 1917012 3838660 34% /

none 2034912 0 2034912 0% /dev/shm

/dev/mapper/VolGroup00-LogVol02

4031680 78712 3748168 3% /home

/dev/mapper/1NEC_____iStorage_2000___00000009279003580008E1

104170 11984 92186 12% /boot/efi

[root@tigre3 hg]# swapon -as

Filename Type Size Used Priority

/dev/mapper/VolGroup00-LogVol00 partition 2064352 0 -1


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With the , before issuing the command, the newly createdLUNs must be created in the low-level Linux tables using the scriptcommand. This command must be carefully used to avoid problems. If you don't knowexactly the parameter values to enter, a system reboot will perform the new configuration

for you without risks.

To use the script:

Determine the fibre-channel host adapters to rescan, by looking into thedirectory

Use the " " ("wide") parameter for high-numbered ports scanning

Limit the LUN range to the needed one,

Run the command with the following syntax (here host4 and host5 are the chosenfibre-channel adapters):

/bin/rescan-scsi-bus.sh -w --hosts=4-5 --luns=0-31

The same command may be used with " " option to remove LUNs in the configuration. Thiscommand must also be used very carefully, as there is a risk to corrupt the system disk (" "directory) when it is used with inadequate parameters. So, it is advised to reboot thesystem to remove LUNs from your configuration.

With the issue the following command on the adapter X:

echo - - - > /sys/class/scsi_host/hostX/scan


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The Multipath system manages only the paths discovered during the boot phase. Tocompensate for the problem we propose a safety mechanism.

After the first boot (after the Multipath installation) StoreWay Multipath checks automaticallythe paths and if the path number on a device is equal to one, a message is logged as inthe example in section 4.2 .

After the next reboots StoreWay Multipath checks automatically the paths and if the pathnumber on a device is lesser than the first boot, a message is logged as in the example insection 4.3.

The command brings back the paths of the multipathingsystem after the physical path(s) reparation.

After a configuration change for example, you can reinitialize the file paths used by thecommand with the following commands sequence:

root# storeway_mpio_check clear

root# storeway_mpio_check init

The Red Hat Enterprise Linux 6 release provides two new path selector algorithms whichdetermine which path to use for the next I/O operation: queue-length and service-time. Thequeue-length algorithm looks at the amount of outstanding I/O to the paths to determinewhich path to use next. The service-time algorithm looks at the amount of outstanding I/Oand the relative throughput of the paths to determine which path to use next.

To change the algorithm, open the file and coment/uncoment thecorresponding lines and execute the following commandes

# multipath -F

# multipath

Or reboot the system.


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The hub mode must be set on the subsystem.

The hub mode must be reset on the subsystem.


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Here is an example of failover/failback messages in file:

Dec 5 11:10:59 tigre3 kernel: lpfc 0000:06:01.0: 0:0203 Nodev timeout on NPortx119ef Data: x2010808 x7 x6Dec 5 11:10:59 tigre3 multipathd: devmap event (2) on1NEC_iStorage_2000_000000092790035800109Dec 5 11:10:59 tigre3 multipathd: 8:48: mark as failedDec 5 11:10:59 tigre3 kernel: SCSI error : return code = 0x10000Dec 5 11:10:59 tigre3 kernel: end_request: I/O error, dev sdd, sector 2922240Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922272): IOerror - error: -5 - bi_rw: 8 - bi_flags: 18 - bi_error: 01000005Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: Failing path 8:48Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922240):Requeued sector as #1Dec 5 11:10:59 tigre3 kernel: end_request: I/O error, dev sdd, sector 2922272

Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922304): IOerror - error: -5 - bi_rw: 8 - bi_flags: 18 - bi_error: 01000005Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922272):Requeued sector as #2Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922336): IOerror - error: -5 - bi_rw: 8 - bi_flags: 18 - bi_error: 01000005Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922304):Requeued sector as #3Dec 5 11:10:59 tigre3 kernel: device-mapper: dm-multipath: 8:48 (#2922368): IOerror - error: -5 - bi_rw: 8 - bi_flags: 18 - bi_error: 01000005Dec 5 11:11:05 tigre3 multipathd: 8:48: readsector0 checker reports path is upDec 5 11:11:05 tigre3 kernel: SCSI error : return code = 0x10000Dec 5 11:11:05 tigre3 multipathd: 8:48: reinstatedDec 5 11:11:05 tigre3 multipathd: devmap event (3)on1NEC_iStorage_2000_000000092790035800109

Jun 1 10:15:54 yack23 StoreWay: Init paths file ...Jun 1 10:16:09 yack23 StoreWay: Init multipath with not enough path with360060160192712008f5027c1f8cbdb11Jun 1 10:16:09 yack23 StoreWay: Init multipath with not enough path with360060160192712008e5027c1f8cbdb11Jun 1 10:16:09 yack23 rc: Starting storeway_mpio: succeeded

Jun 1 13:03:54 yack23 StoreWay: Check paths ...Jun 1 13:04:08 yack23 StoreWay: Degraded multipath with360060160192712008f5027c1f8cbdb11 (dm-13 )Jun 1 13:04:08 yack23 StoreWay: Degraded multipath with360060160192712008e5027c1f8cbdb11 (dm-12 )


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Aug 6 08:37:12 zeta14 kernel: connection1:0: ping timeout of 5 secs expired, lastrx 4791894917, last ping 4791899917, now 4791904917Aug 6 08:37:12 zeta14 kernel: connection1:0: detected conn error (1011)Aug 6 08:37:12 zeta14 multipathd: sddm: tur checker reports path is downAug 6 08:37:12 zeta14 kernel: device-mapper: multipath: Failing path 71:64.Aug 6 08:37:12 zeta14 iscsid: Kernel reported iSCSI connection 1:0 error (1011)state (3)Aug 6 08:37:51 zeta14 iscsid: connect failed (113)Aug 6 08:37:57 zeta14 iscsid: connect failed (113)Aug 6 08:38:00 zeta14 multipathd: dm-92: add map (uevent)Aug 6 08:38:00 zeta14 iscsid: connection1:0 is operational after recovery (5attempts)Aug 6 08:38:05 zeta14 multipathd: 71:64: reinstatedAug 6 08:38:05 zeta14 multipathd: dm-92: add map (uevent)


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The command displays information on the SCSI hosts and devices.

-h displays the present Help-o Object Device machine list

-O Object Device machine list verbose

The lines display:

Host host name

Ven Vendor (3 ASCII characters)

FW Firmware version

Ver Driver version

DID switchDomain, portId, loopId (with brocade device)

WWN host WorldWideName

The lines display:

Tgt Target identificator

Ven Vendor Name

Mod Target model (if available)

WWN Target WorldWideName

DID switchDomain, portId, loopId (with brocade device)

The columns display:

Device Identify the Linux device name (sd/raw/sg)

State Device state (test unit ready / reservation).

OK => device ready

NOK => device not ready

*OK => device ready and registered

!OK => device ready and reserved

Parent scsi name of the device

Ven Vendor (3 ASCII characters)

Type Device type returned by Inquiry

MB Capacity in M bytes

dev major, minor device

sid Target Id (Decimal)lun Lun (from 0 to 31)

Qd retrieve the actual Queue Depth

Ty (HDS, SYMM, DGC, STK) Device Type (R5,Rs,R1,R0,R6+, i, B for BCV)

Port Subsystem attachment Port name

DEV Device number inside the subsystem

(EMC) Symmetrix DEV Id

Comment : (DGC) Assigned or NotAssignedSupported subsystems:

EMC: Symmetrix up to Symm7, DAS CX/AX

NEC: Series 1000 & 2000, Optima5000


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NetApp: 270, 30xx

The lines display:Device Identify the device partition name (ex: sda1)State Partition state

Ex: BSY => busyEx: IDL => idle

Ven Partition type (primary, extended, logical)MB Capacity in M bytesdev major, minor device

The lines display:

Fs Filesystem identiticator (ex: fs0)

Label Filesystem label

Type Filesystem type (ext3, xfs etc...)

BSF Block space free (%)

ISF Inode space free (%)

The part displays and information:

The lines display:

Device Identify the Linux device-mapper name (dm-#)

alias Identify the persistante name (link) to the dm-#

mirrors Mirrors number

log Log type {core or disk}

sync Sync type {sync or nosync}

The next lines describe the mirror components

The lines display:Device Identify the Linux device-mapper name (dm-#)

Alias Identify the persistant name (link) to the dm-#

Pg Priority group number

Path Path number

Type multipath type (fo=failover, lb=loadbalancing)

The lines display:

pgrp# Identify Priority group number

path Path number per Priority group

stat Priority group status

The lines display:

Device Identify the path name (tgt:/dev/sdx)

Status path status

tur test unit ready result

fail fail counter


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The part displays Logical Volume Group information:

The lines display:

VG Identify the volume group name

Size volume group size

Status volume group status

Deps volume group dependence

The lines display:

LV Identify the logical volume name

dm associated device-mapper name

size logical volume size

type logical volume type

status logical volume status

deps logical volume dependence

The lines display:

Fs Filesystem identiticator (ex: fs0)Label Filesystem label

Type Filesystem type (ext3, xfs etc...)

BSF Block space free (%)

ISF Inode space free (%)

#Copyright (C) by BULL 2003,2006#cmd: 0.1.2#lib: 2.1.3 all rights reserved.#

============== ADP info ======================eth0 == NEC == FW:? V:? == IP@:172.16.101.56 = MAC:00:00:4c:71:3f:10eth1 == Int == FW:? V:? == IP@:192.168.1.56 = MAC:00:03:47:e0:79:b8eth2 == ZNY == FW:? V:? == IP@:192.168.2.56 = MAC:00:c0:95:f8:8c:14lo == XER == FW:? V:? == MAC:00:00:00:00:00:00sit0 == XER == FW:? V:? == MAC:00:00:00:00host0 == scsi0 ADP == FW:? V:6.2.36 ==host1 == scsi1 ADP == FW:? V:6.2.36 ==st0 OK == sg0 , raw? == TANDBERG TDC 4222 Bull 5,0

host2 == scsi2 EMU == FW:1.90A3 (E2M1.90A3) V:8.0.16.17 == DID:30600 =20000000c93fcdef:0x10000000c93fcdeftgt2.0 == NETWORK APPLIANCE CORP. == FAS3020 == WWN:500a09808617b917:500a09818617b917 =

DID:030400sda OK == sg1 , raw? == NETAPP LUN 10240 8,0 0,0 30sdb OK == sg2 , raw? == NETAPP LUN 10240 8,16 0,1 30

tgt2.1 == XYRATEX == Optima1200 == WWN:20000050cc2000b8:23000050cc2000b8 =DID:030c00

sdc OK == sg3 , raw? == XYRATEX F5402E 9540 8,32 1,0 30 R? 2

sdd OK == sg4 , raw? == XYRATEX F5402E 9540 8,48 1,1 30 R? 3ses0 OK == sg5 , raw? == XYRATEX F5402E 1,2

tgt2.2 == EMC CORPORATION == Symm7 == WWN:50060482d52cda47:50060482d52cda47 =DID:000000

sde OK == sg6 , raw? == EMC SYMMETRIX 8631 8,64 2,0 30 QT 0080sdf OK == sg7 , raw? == EMC SYMMETRIX 8631 8,80 2,1 30 QT 0081sdg OK == sg8 , raw? == EMC SYMMETRIX 8631 8,96 2,2 30 QT 0082sdh OK == sg9 , raw? == EMC SYMMETRIX 8631 8,112 2,3 30 QT 0083sdi OK == sg10 , raw? == EMC SYMMETRIX 8631 8,128 2,4 30 QT 0084sdj OK == sg11 , raw? == EMC SYMMETRIX 8631 8,144 2,5 30 QT 0085sdk OK == sg12 , raw? == EMC SYMMETRIX 8631 8,160 2,6 30 QT 0086sdl OK == sg13 , raw? == EMC SYMMETRIX 8631 8,176 2,7 30 QT 0087sdm OK == sg14 , raw? == EMC SYMMETRIX 8631 8,192 2,8 30 QT 0088sdn OK == sg15 , raw? == EMC SYMMETRIX 8631 8,208 2,9 30 QT 0089

tgt2.3 == NEC CORPORATION == 2300 == WWN:200000004c7f0445:210000004c7f0445 =DID:0019ef

sdo OK == sg16 , raw? == NEC iStorage 2000 8533 8,224 3,0 30 R1 0109

sdp OK == sg17 , raw? == NEC iStorage 2000 8533 8,240 3,1 30 R1 010A


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host3 == scsi3 EMU == FW:1.00A4 (H2D1.00A4) V:8.0.16.17 == DID:30700 =20000000c93393dc:0x10000000c93393dctgt3.0 == NETWORK APPLIANCE CORP. == FAS3020 == WWN:500a09808617b917:500a098a8617b917 =

DID:030900sdq OK == sg18 , raw? == NETAPP LUN 10240 65,0 0,0 30sdr OK == sg19 , raw? == NETAPP LUN 10240 65,16 0,1 30

tgt3.1 == XYRATEX == Optima1200 == WWN:20000050cc2000b8:22000050cc2000b8 =DID:030d00

sds OK == sg20 , raw? == XYRATEX F5402E 9540 65,32 1,0 30 R? 2sdt OK == sg21 , raw? == XYRATEX F5402E 9540 65,48 1,1 30 R? 3

ses1 OK == sg22 , raw? == XYRATEX F5402E 1,2tgt3.2 == EMC CORPORATION == Symm7 == WWN:50060482d52cda49:50060482d52cda49 =DID:000400

sdu OK == sg23 , raw? == EMC SYMMETRIX 8631 65,64 2,0 30 QT 0080sdv OK == sg24 , raw? == EMC SYMMETRIX 8631 65,80 2,1 30 QT 0081sdw OK == sg25 , raw? == EMC SYMMETRIX 8631 65,96 2,2 30 QT 0082sdx OK == sg26 , raw? == EMC SYMMETRIX 8631 65,112 2,3 30 QT 0083sdy OK == sg27 , raw? == EMC SYMMETRIX 8631 65,128 2,4 30 QT 0084sdz OK == sg28 , raw? == EMC SYMMETRIX 8631 65,144 2,5 30 QT 0085sdaa OK == sg29 , raw? == EMC SYMMETRIX 8631 65,160 2,6 30 QT 0086sdab OK == sg30 , raw? == EMC SYMMETRIX 8631 65,176 2,7 30 QT 0087sdac OK == sg31 , raw? == EMC SYMMETRIX 8631 65,192 2,8 30 QT 0088sdad OK == sg32 , raw? == EMC SYMMETRIX 8631 65,208 2,9 30 QT 0089

tgt3.3 == NEC CORPORATION == 2300 == WWN:200000004c7f0445:230000004c7f0445 =DID:001ce8

sdae OK == sg33 , raw? == NEC iStorage 2000 8533 65,224 3,0 30 R1 0109sdaf OK == sg34 , raw? == NEC iStorage 2000 8533 65,240 3,1 30 R1 010A

host4 == scsi4 FW:3.00.00.04 V:5.00.04 == iqn.2000-04.com.qlogic:qla4010.fs20517b00891

rdc0 == DAC == FW:4.07-0-29 V:2.5.47 ==c0d0 OK == raw? == Disk RAID-5 48,0c0d1 OK == raw? == Disk RAID-7 48,8

============== MPIO info ======================dm-3 == SEMC_____SYMMETRIX______100329089000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdad == active Ready == failcount 2/dev/sdn == active Ready == failcount 3

dm-9 == 320030050cc2000b8 = 2 pg/2 paths fopgrp 0 == 1 paths == enabled/dev/sdd == active Ready == failcount 2

pgrp 1 == 1 paths == active/dev/sdt == active Ready == failcount 0

dm-10 == SEMC_____SYMMETRIX______100329080000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sde == active Ready == failcount 3

/dev/sdu == active Ready == failcount 2dm-14 == SEMC_____SYMMETRIX______100329084000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdi == active Ready == failcount 3/dev/sdy == active Ready == failcount 2

dm-7 == 360a9800043346234525a356f61395478 = 2 pg/2 paths fopgrp 0 == 1 paths == active/dev/sdb == active Ready == failcount 5 == main ok

pgrp 1 == 1 paths == enabled/dev/sdr == active Ready == failcount 4 == backup ok

dm-2 == SEMC_____SYMMETRIX______100329088000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdac == active Ready == failcount 2/dev/sdm == active Ready == failcount 3

dm-4 == 1NEC_____iStorage_2000___000000092790035800109 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdae == active Ready == failcount 2/dev/sdo == active Ready == failcount 2

dm-13 == SEMC_____SYMMETRIX______100329083000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdh == active Ready == failcount 4/dev/sdx == active Ready == failcount 3

dm-8 == 320020050cc2000b8 = 2 pg/2 paths fopgrp 0 == 1 paths == enabled/dev/sdc == active Ready == failcount 2

pgrp 1 == 1 paths == active/dev/sds == active Ready == failcount 0

dm-1 == SEMC_____SYMMETRIX______100329087000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdab == active Ready == failcount 2/dev/sdl == active Ready == failcount 3

dm-6 == 360a9800043346234525a356f47566d33 = 2 pg/2 paths fopgrp 0 == 1 paths == active/dev/sda == active Ready == failcount 5 == main ok

pgrp 1 == 1 paths == enabled

/dev/sdq == active Ready == failcount 4 == backup ok


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dm-12 == SEMC_____SYMMETRIX______100329082000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdg == active Ready == failcount 3/dev/sdw == active Ready == failcount 2

dm-5 == 1NEC_____iStorage_2000___00000009279003580010A = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdaf == active Ready == failcount 2/dev/sdp == active Ready == failcount 2

dm-0 == SEMC_____SYMMETRIX______100329086000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active

/dev/sdaa == active Ready == failcount 2/dev/sdk == active Ready == failcount 3dm-11 == SEMC_____SYMMETRIX______100329081000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdf == active Ready == failcount 3/dev/sdv == active Ready == failcount 2

dm-15 == SEMC_____SYMMETRIX______100329085000 = 1 pg/2 paths lbpgrp 0 == 2 paths == active/dev/sdj == active Ready == failcount 3/dev/sdz == active Ready == failcount 2

============== LVM info ======================VG1 == 16.66 GB = resizable == sdo sdae sdp sdaflvol0 (dm-16) == 3.00 GB = linear = available = dm-4

#Copyright (C) by BULL 2003-2009#cmd: 0.2.4#lib: 2.2.8 all rights reserved.#============== ADP info ======================eth0 == ??? = up = FW:? V:? == IP@:192.168.95.8 = MAC:00:15:17:6c:47:e4eth1 == ??? = up = FW:? V:? == IP@:192.168.1.102 = MAC:00:16:97:c4:a9:b4eth2 == ??? = up = FW:? V:? == IP@:192.168.0.103 = MAC:00:15:17:6c:47:e5eth3 == ??? = unknown = FW:? V:? == MAC:00:16:97:c4:a9:b5lo == XER = unknown = FW:? V:? == MAC:00:00:00:00:00:00...host5 == scsi5 sys0 == FW:? V:? ==

ssn1 == ISCSI Session == Optima1500 == IQN:iqn.2001-03.jp.nec:storage01:ist-3-10-sn-0000000935082027.lx-rhel00.target0000

cnx1-0 == ISCSI Connection == 192.168.0.35:3260 [eth2]sddl OK == sg118, raw? == NEC iStorage 1000 1.6GB 71,48 0,0 32 R0 0001sddm OK == sg119, raw? == NEC iStorage 1000 1.6GB 71,64 0,1 32 R0 0002

host6 == scsi6 sys0 == FW:? V:? ==ssn2 == ISCSI Session == Optima1500 == IQN:iqn.2001-03.jp.nec:storage01:ist-3-10-sn-0000000935082027.lx-

rhel00.target0000cnx2-0 == ISCSI Connection == 192.168.1.35:3260 [eth1]sddn OK == sg120, raw? == NEC iStorage 1000 1.6GB 71,80 0,0 32 R0 0001sddo OK == sg121, raw? == NEC iStorage 1000 1.6GB 71,96 0,1 32 R0 0002

...===========-== DM info =======================...

dm-92 == 20030138419850002 = 2 pg/2 paths fopgrp 0 == 1 paths == activessn1:/dev/sddm == active Ready == failcount 4

pgrp 1 == 1 paths == enabledssn2:/dev/sddo == active Ready == failcount 0

dm-93 == 20030138419850001 = 2 pg/2 paths fopgrp 0 == 1 paths == active

ssn1:/dev/sddl == active Ready == failcount 4pgrp 1 == 1 paths == enabled

ssn2:/dev/sddn == active Ready == failcount 0...============== LVM info =======================...


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http://christophe.varoqui.free.fr/multipath.html

http://sources.redhat.com/dm

For RHEL6: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/DM_Multipath/index.html

LVM-HOWTO, CD 4:

/usr/share/doc/howto/en/txt/LVM-HOWTO.gz/usr/share/doc/howto/en/html/LVM-HOWTO/index.html

http://sourceware.org/lvm

For RHEL6: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/index.html

http://christophe.varoqui.free.fr/multipath.htmlhttp://sources.redhat.com/dmhttp://sourceware.org/lvmhttp://christophe.varoqui.free.fr/multipath.htmlhttp://sources.redhat.com/dmhttp://sourceware.org/lvm

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The alias is the name of a Multipath device. By default, the alias is set to the WWID.However, by setting the "user_friendly_names" configuration option, the alias is set to aunique name of the form mpath. The alias name can also be explicitly set for each

Multipath device in the configuration file.

NOTE: While the alias in guaranteed to be unique on a node, it is not guaranteed to bethe same on all nodes using the Multipath device. Also, it may change.

At regular intervals, multipathd checks the current priority of all path groups. If the currentpath group is not the highest priority path group, multipathd reacts according to thefailback mode.By default, multipathd immediately switches to the highest priority path group. Otheroptions for multipathd are to (a) wait for a user-defined length of time (for the path groups

to stabilize) and then switch or (b) for multipathd to do nothing and wait for manualintervention. Failback can be forced at any time by running the multipath command.

When I/O to a path fails, the dm-multipath module tries to switch to an enabled pathgroup. If there are no enabled path groups with any paths in the ready state, dm-multipathtries to switch to a disabled path group. If necessary, dm-multipath runs the hardwarehandler for the Multipath device.

A kernel module that performs hardware-specific actions when switching path groups and

dealing with I/O errors.

The Multipath device is the device mapper device created by dm-multipath. A Multipathdevice can be identified by either its WWID or its alias. A Multipath device has one ormore path groups. It also has numerous attributes defined in the following file:/usr/share/doc/device-mapper-multipathd-0.4.5/multipath.conf.annotated.

The connection from an HBA port to a storage controller port for a LUN. Each pathappears as a separate device. Paths can be in various states (refer to "Path States").

A grouping of paths. With DM-MP, only one path group--the active path group--receivesI/O at any time. Within a path group, DM-MP selects which ready path should receive I/Oin a round robin fashion. Path groups can be in various states (refer to "Path GroupStates").

Each path group has a priority that is equal to the sum of the priorities of all the non-faultypaths in the group. By default, the multipathd daemon tries to ensure that the path groupwith the highest priority is always in the active state.


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- Path group currently receiving I/O requests.- Path groups to try if the active path group has no paths in the ready state.- Path groups to try if the active path group and all enabled path groups have no

paths in the active state.

NOTE: The disabled state only exists for certain storage arrays.

Each path can have a priority assigned to it by a callout program. Path priorities can beused to group paths by priority and change their relative weights for the round robin pathselector.

- Path is able to handle I/O requests.- Path is up, but temporarily not available for normal operations.

- Path is unable to handle I/O requests.

- Path is a passive path, on an active/passive controller.

NOTE: The shaky and ghost states only exist for certain storage arrays.

The WWID (World Wide Identifier) is an identifier for the Multipath device that isguaranteed to be globally unique and unchanging. It is determined by the getuid calloutprogram.


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