RHEL5 多路徑配置

1     檢查軟件包是否安裝

[root@pcvmaster ~]# rpm -qa|grep device-mapper

device-mapper-libs-1.02.74-10.el6.x86_64

device-mapper-event-libs-1.02.74-10.el6.x86_64

device-mapper-multipath-0.4.9-56.el6.x86_64

device-mapper-1.02.74-10.el6.x86_64

device-mapper-event-1.02.74-10.el6.x86_64

device-mapper-multipath-libs-0.4.9-56.el6.x86_64

2     安裝multipath

[root@pcvmaster ~]# yum -yinstall multipath

3     開機啓動

[root@pcvmaster ~]# chkconfigmultipathd on

4     編輯multipath配置文件

vi /etc/multipath.conf

# This is a basicconfiguration file with some examples, for device mapper

# multipath.

# For a complete list of thedefault configuration values, see

#/usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.defaults

# For a list of configurationoptions with descriptions, see

#/usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.annotated

#

# REMEMBER: After updatingmultipath.conf, you must run

#

# service multipathd reload

#

# for the changes to takeeffect in multipathd

 

## By default, devices withvendor = "IBM" and product = "S/390.*" are

## blacklisted. To enablemulitpathing on these devies, uncomment the

## following lines.

#blacklist_exceptions {

#      device {

#             vendor "IBM"

#             product "S/390.*"

#      }

#}

 

## Use user friendly names,instead of using WWIDs as names.

defaults {

       user_friendly_names yes

}

##

## Here is an example of howto configure some standard options.

##

#

#defaults {

#      udev_dir              /dev

#      polling_interval      10

#      selector              "round-robin0"

#      path_grouping_policy  multibus

#      getuid_callout        "/lib/udev/scsi_id--whitelisted --device=/dev/%n"

#      prio                  alua

#      path_checker          readsector0

#      rr_min_io             100

#      max_fds               8192

#      rr_weight             priorities

#      failback              immediate

#      no_path_retry         fail

#      user_friendly_names   yes

#}

##

## The wwid line in thefollowing blacklist section is shown as an example

## of how to blacklistdevices by wwid.  The 2 devnode lines arethe

## compiled in defaultblacklist. If you want to blacklist entire types

## of devices, such as allscsi devices, you should use a devnode line.

## However, if you want toblacklist specific devices, you should use

## a wwid line.  Since there is no guarantee that a specificdevice will

## not change names on reboot(from /dev/sda to /dev/sdb for example)

## devnode lines are notrecommended for blacklisting specific devices.

##

#blacklist {

#       wwid 26353900f02796769

#      devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"

#      devnode "^hd[a-z]"

#}

#multipaths {

#      multipath {

#             wwid                  3600508b4000156d700012000000b0000

#             alias                 yellow

#             path_grouping_policy  multibus

#             path_checker          readsector0

#             path_selector         "round-robin0"

#             failback              manual

#             rr_weight             priorities

#             no_path_retry         5

#      }

#      multipath {

#             wwid                  1DEC_____321816758474

#             alias                 red

#      }

#}

#devices {

#      device {

#             vendor                "COMPAQ  "

#             product               "HSV110(C)COMPAQ"

#             path_grouping_policy  multibus

#             getuid_callout         "/lib/udev/scsi_id --whitelisted --device=/dev/%n"

#             path_checker          readsector0

#             path_selector         "round-robin0"

#             hardware_handler      "0"

#             failback              15

#             rr_weight             priorities

#             no_path_retry         queue

#      }

#      device {

#             vendor                "COMPAQ  "

#             product               "MSA1000         "

#             path_grouping_policy  multibus

#      }

#}

 

blacklist {
devnode "^(ram|raw|loop|fd|md|dm-|sr|sr|scd|st)[0-9]*"
devnode "^hd[a-z]"
}
devices {
device {
vendor "Netapp"
path_grouping_policy multibus
features "1 queue_if_no_path"
path_checker readsector()
failback immediate
}
}

5     啓動服務

[root@pcvmaster ~]#/etc/init.d/multipathd start

6     刪除現有沒有使用的路徑

[root@pcvmaster ~]# multipath–F

7     格式化路徑，檢測路徑，合併路徑

[root@pcvmaster ~]# multipath-v2

8     查看多路徑狀態

[root@pcvmaster ~]# multipath–ll

9     重啓系統

[root@pcvmaster ~]# reboot

10建立PV多塊磁盤,

[root@pcvmaster ~]# pvcreate/dev/mapper/mpath{d,f,e,p,t,k,j,c,s,q}

11添加多塊磁盤到Volbackup

[root@pcvmaster~]# vgcreateVolbackup /dev/mapper/mpath{d,f,e,p,t,k,j,c,s,q}

12建立LV

[root@pcvmaster ~]# lvcreate-l 1310780 -n LogVol01 Volbackup

13格式化LV

[root@pcvmaster ~] mkfs.ext4/dev/Volbackup/LogVol01

14掛載

[root@pcvmaster ~]# mount/dev/Volbackup/LogVol01 /backup

15FAQ

15.1  模塊沒有加載成功後

若是模塊沒有加載成功請使用下列命初始化DM，或重啓系統

---Use thefollowing commands to initialize and start DM for the first time:

# modprobedm-multipath

# modprobe dm-round-robin

# servicemultipathd start

# multipath –v2

15.2  multipath原理介紹

一、device-mapper-multipath：即multipath-tools。主要提供multipathd和multipath等工具和 multipath.conf等配置文件。這些工具經過device mapper的ioctr的接口建立和配置multipath設備（調用device-mapper的用戶空間庫。建立的多路徑設備會在/dev/mapper中）。

 

二、device-mapper：主要包括兩大部分：內核部分和用戶部分。內核部分主要由device mapper核心（dm.ko）和一些target driver（md-multipath.ko）。核心完成設備的映射，而target根據映射關係和自身特色具體處理從mappered device 下來的i/o。同時，在覈心部分，提供了一個接口，用戶經過ioctr可和內核部分通訊，以指導內核驅動的行爲，好比如何建立mappered device，這些divece的屬性等。linux device mapper的用戶空間部分主要包括device-mapper這個包。其中包括dmsetup工具和一些幫助建立和配置mappered device的庫。這些庫主要抽象，封裝了與ioctr通訊的接口，以便方便建立和配置mappered device。multipath-tool的程序中就須要調用這些庫。

 

三、dm-multipath.ko和dm.ko：dm.ko是devicemapper驅動。它是實現multipath的基礎。dm-multipath實際上是dm的一個target驅動。

 

四、scsi_id：包含在udev程序包中，能夠在multipath.conf中配置該程序來獲取scsi設備的序號。經過序號，即可以判斷多個路徑對應了同一設備。這個是多路徑實現的關鍵。scsi_id是經過sg驅動，向設備發送EVPD page80或page83 的inquery命令來查詢scsi設備的標識。但一些設備並不支持EVPD 的inquery命令，因此他們沒法被用來生成multipath設備。但能夠改寫scsi_id，爲不能提供scsi設備標識的設備虛擬一個標識符，並輸出到標準輸出。multipath程序在建立multipath設備時，會調用scsi_id，從其標準輸出中得到該設備的scsi id。在改寫時，須要修改scsi_id程序的返回值爲0。由於在multipath程序中，會檢查該直來肯定scsi id是否已經成功獲得。