1 检查软件包是否安装[root@pcvmaster ~]# rpm -qa|grep device-mapperdevice-mapper-libs-1.02.74-10.el6.x86_64device-mapper-event-libs-1.02.74-10.el6.x86_64device-mapper-multipath-0.4.9-56.el6.x86_64device-mapper-1.02.74-10.el6.x86_64device-mapper-event-1.02.74-10.el6.x86_64device-mapper-multipath-libs-0.4.9-56.el6.x86_642 安装multipath[root@pcvmaster ~]# yum -yinstall multipath3 开机启动[root@pcvmaster ~]# chkconfigmultipathd on4 编辑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_policymultibusfeatures “1queue_if_no_path”path_checkerreadsector()failback immediate}}5 启动服务[root@pcvmaster ~]#/etc/init.d/multipathd start6 删除现有没有使用的路径[root@pcvmaster ~]# multipath–F7 格式化路径，检测路径，合并路径[root@pcvmaster ~]# multipath-v28 查看多路径状态[root@pcvmaster ~]# multipath–ll9 重启系统[root@pcvmaster ~]# reboot10创建PV多块磁盘,[root@pcvmaster ~]# pvcreate/dev/mapper/mpath{d,f,e,p,t,k,j,c,s,q}11添加多块磁盘到Volbackup[root@pcvmaster~]# vgcreateVolbackup /dev/mapper/mpath{d,f,e,p,t,k,j,c,s,q}12创建LV[root@pcvmaster ~]# lvcreate-l 1310780 -n LogVol01 Volbackup13格式化LV[root@pcvmaster ~] mkfs.ext4/dev/Volbackup/LogVol0114挂载[root@pcvmaster ~]# mount/dev/Volbackup/LogVol01 /backup15FAQ15.1 模块没有加载成功后如果模块没有加载成功请使用下列命初始化DM，，或重启系统—Use thefollowing commands to initialize and start DM for the first time:# modprobedm-multipath# modprobe dm-round-robin# servicemultipathd start# multipath –v215.2 multipath原理介绍1、device-mapper-multipath：即multipath-tools。主要提供multipathd和multipath等工具和 multipath.conf等配置文件。这些工具通过device mapper的ioctr的接口创建和配置multipath设备（调用device-mapper的用户空间库。创建的多路径设备会在/dev/mapper中）。2、device-mapper：主要包括两大部分：内核部分和用户部分。内核部分主要由device mapper核心（dm.ko）和一些target driver（md-multipath.ko）。核心完成设备的映射，而target根据映射关系和自身特点具体处理从mappered device 下来的i/o。同时，在核心部分，提供了一个接口，用户通过ioctr可和内核部分通信，以指导内核驱动的行为，比如如何创建mappered device，这些divece的属性等。linux device mapper的用户空间部分主要包括device-mapper这个包。其中包括dmsetup工具和一些帮助创建和配置mappered device的库。这些库主要抽象，封装了与ioctr通信的接口，以便方便创建和配置mappered device。multipath-tool的程序中就需要调用这些库。3、dm-multipath.ko和dm.ko：dm.ko是devicemapper驱动。它是实现multipath的基础。dm-multipath其实是dm的一个target驱动。4、scsi_id：包含在udev程序包中，可以在multipath.conf中配置该程序来获取scsi设备的序号。通过序号，便可以判断多个路径对应了同一设备。这个是多路径实现的关键。scsi_id是通过sg驱动，向设备发送EVPD page80或page83 的inquery命令来查询scsi设备的标识。但一些设备并不支持EVPD 的inquery命令，所以他们无法被用来生成multipath设备。但可以改写scsi_id，为不能提供scsi设备标识的设备虚拟一个标识符，并输出到标准输出。multipath程序在创建multipath设备时，会调用scsi_id，从其标准输出中获得该设备的scsi id。在改写时，需要修改scsi_id程序的返回值为0。因为在multipath程序中，会检查该直来确定scsi id是否已经成功得到。
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