1.确保安装以下的包：
device-mapper
device-mapper-multipath
[root@nticket1~]# rpm -qa "*device*"
device-mapper-multipath-0.4.9-56.0.3.el5
device-mapper-multipath-libs-0.4.9-56.0.3.el5
device-mapper-1.02.67-2.el5
device-mapper-event-1.02.67-2.el5
device-mapper-1.02.67-2.el5
2.编辑配置文件/etc/multipath.conf
要创建一个multipath.conf的配置文件，该文件在安装后不会自动创建。可以使用一个模板创建一个multipath.conf的文件。
[root@nticket1 ~]# cp /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf.synthetic /etc/multipath.conf
defaults
{
user_friendly_names yes
max_fds max
queue_without_daemon no
flush_on_last_del yes
}
devices {
device {
vendor "HUAWEI "
product "S2300E"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s/block/%n"
path_checker directio
path_selector "round-robin 0"
hardware_handler "0"
failback 15
rr_weight priorities
no_path_retry queue
rr_min_io 100
product_blacklist LUNZ
}
}
3.加载并启动multipath模块和服务
# modprobe dm_multipath
# lsmod |grep dm_multipath
dm_multipath 19157 0
dm_mod 81987 3 dm_multipath,dm_mirror,dm_log
# service multipathd restart
# chkconfig --level 345 multipathd on
# chkconfig --list | grep multipathd
multipathd 0:关闭 1:关闭 2:关闭 3:启用 4:启用 5:启用 6:关闭
# multipath -v3 //装配多路径设备
4.检查multipath聚合后的设备名，以及设备对应的链路情况。
[root@nticket1~]# multipath -ll //显示当前多路径拓扑结构
Dec 20 16:31:21| multipath.conf line 73, invalid keyword: {
mpath2 (360022a11000659d858abb41000000001)dm-1 HUAWEI,S2300E
size=200G features='0' hwhandler='0' wp=rw
|-+-policy='round-robin 0' prio=1 status=active
| `- 1:0:0:1 sdc8:32 active ready running
|-+-policy='round-robin 0' prio=1 status=enabled
| `- 1:0:1:1 sde8:64 active ready running
|-+-policy='round-robin 0' prio=1 status=enabled
| `- 2:0:0:1 sdg8:96 active ready running
`-+-policy='round-robin 0' prio=1 status=enabled
`- 2:0:1:1 sdi 8:128 active ready running
mpath1 (360022a11000659d858abb3f200000000) dm-0 HUAWEI,S2300E
size=200G features='0' hwhandler='0' wp=rw
|-+-policy='round-robin 0' prio=1 status=active
| `- 1:0:0:0 sdb8:16 active ready running
|-+-policy='round-robin 0' prio=1 status=enabled
| `- 1:0:1:0 sdd8:48 active ready running
|-+- policy='round-robin0' prio=1 status=enabled
| `- 2:0:0:0 sdf8:80 active ready running
`-+-policy='round-robin 0' prio=1 status=enabled
`- 2:0:1:0 sdh 8:112 active ready running
以上的结果可以看出，每个磁盘设备对应的是4条链路。每个设备都有两个multipath设备名，分别是mpath[x]和dm-[x]，mpath位于/dev/mpath目录下，dm-[x]位于/dev目录下。
[root@nticket1 dev]# ls dm*
dm-0 dm-1
[root@nticket1 mpath]# ll
总计 0
lrwxrwxrwx 1 root root 7 12-20 15:01 360022a11000659d858abb3f200000000 -> ../dm-0
lrwxrwxrwx 1 root root 7 12-20 15:01 360022a11000659d858abb41000000001 -> ../dm-1
配置正确的话就会在/dev/mapper/目录下多出mpath1、mpath2等之类设备
[root@nticket1 ~]# cd /dev/mapper/
[root@nticket1 mapper]# ll
总计 0
crw------- 1 root root 10, 236 12-2010:32 control
brw-rw---- 1 root disk 252, 0 12-2015:01 mpath1
brw-rw---- 1 root disk 252, 1 12-2015:01 mpath2
用fdisk -l命令也可以看到多路径软件创建的磁盘，如下面中的/dev/dm-[0-1]
[root@nticket1 mapper]# fdisk -l
Disk /dev/sda: 1127.4 GB, 1127428915200 bytes
255 heads, 63 sectors/track, 137068 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 130694 1049695132+ 83 Linux
/dev/sda3 130695 137068 51199155 82 Linux swap / Solaris
Disk /dev/sdb: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdb doesn't contain a valid partition table
......
......
Disk /dev/sdi: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdi doesn't contain a valid partition table
Disk /dev/dm-0: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-0 doesn't contain a valid partition table
Disk /dev/dm-1: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/dm-1 doesn't contain a valid partition table
5.multipath磁盘的基本操作
要对多路径软件生成的磁盘进行操作直接操作/dev/mapper/目录下的磁盘就行,
在对多路径软件生成的磁盘进行分区之前最好运行一下pvcreate命令:
# pvcreate /dev/mapper/mpath1
# fdisk /dev/mapper/mpath1
用fdisk对多路径软件生成的磁盘进行分区保存时会有一个报错,此报错不用理会，
这时所生成的磁盘分区没有马上添加到/dev/mapper目录下。
[root@nticket1 mapper]# ls
control mpath1 mpath2
此时需要重启IPSAN或者FCSAN的驱动，或重启服务器，完成后会看到分区盘。
[root@nticket1 mapper]# ls
control mpath1 mpath1p1 mpath2 mpath1p2
上面是一个简单的multipath配置，分区完成后就可以对mpath1p1、mpath2p1进行使用了，如格式化挂载到文件系统，或提供ASM使用。如下：
# mkfs.ext3 /dev/mapper/mpath0p1 #对mpath1p1分区格式化成ext3文件系统
# mount /dev/mapper/mpath0p1 /ipsan/ #挂载mpath1p1分区
[root@racdb1 mapper]# mkfs.ext3 /dev/mapper/mpath8
[root@racdb1 mapper]# mkdir /test1
[root@racdb1 mapper]# mount /dev/mapper/mpath8 /test1
[root@testdb ~]# vi /etc/fstab
/dev/mapper/mpath8 /test1 ext3 defaults 0 0
6.路径切换测试
最后可以通过拔掉存储和SAN光纤交换机之间的光纤，或交换机和服务机之间的光纤来测试路径切换，使用iostat查看测试。
相关命令和参数详细说明参考下面的几篇文章：
http://blog.itpub.net/23135684/viewspace-745789
http://blog.csdn.net/lichangzai/article/details/17501035
转自http://blog.csdn.net/lichangzai/article/details/17501355