一、多路径解释
多路径，顾名思义就是有多种选择的路径。在SAN或IPSAN环境，主机和存储之间外加了光纤交换机，这就导致主机和存储之间交换速度和效率增强，一条路径肯定是不行的，也是不安全不稳定的。多路径就是要来解决从主机到磁盘之间最快，最高效的问题。主要实现如下几个功能
- 故障的切换和恢复
- IO流量的负载均衡
- 磁盘的虚拟化
多路径之前一直是存储厂商负责解决，竟来被拆分出来单独卖钱了。
构架基本是这样的：存储，多路径软件，光纤交换机，主机，主机系统。
二、LINUX下的multipath
1、查看是否自带安装？
[root@web2 multipath]# rpm -qa|grep device device-mapper-1.02.39-1.el5 device-mapper-1.02.39-1.el5 device-mapper-multipath-0.4.7-34.el5 device-mapper-event-1.02.39-1.el5 [root@web2 multipath]#
2、安装
rpm -ivh device-mapper-1.02.39-1.el5.rpm #安装映射包 rpm -ivh device-mapper-multipath-0.4.7-34.el5.rpm #安装多路径包 外加加入开机启动 chkconfig –level 2345 multipathd on #设置成开机自启动multipathd lsmod |grep dm_multipath #来检查安装是否正常
3、配置
# on the default devices.
blacklist {
devnode "^(ram|raw|loop|fd|md|dm-|sr|sr|scd|st)[0-9]*"
devnode "^hd[a-z]"
}
devices {
device {
vendor "HP"
path_grouping_policy multibus
features "1 queue_if_no_path"
path_checker readsector()
failback immediate
}
}
完整的配置如下：
blacklist {
devnode "^sda"
}
defaults {
user_friendly_names no
}
multipaths {
multipath {
wwid 14945540000000000a67854c6270b4359c66c272e2f356321
alias iscsi-dm0
path_grouping_policy multibus
path_checker tur
path_selector "round-robin 0"
}
multipath {
wwid 14945540000000000dcca2eda91d70b81edbcfce2357f99ee
alias iscsi-dm1
path_grouping_policy multibus
path_checker tur
path_selector "round-robin 0"
}
multipath {
wwid 1494554000000000020f763489c165561101813333957ed96
alias iscsi-dm2
path_grouping_policy multibus
path_checker tur
path_selector "round-robin 0"
}
multipath {
wwid 14945540000000000919ca813020a195422ba3663e1f03cc3
alias iscsi-dm3
path_grouping_policy multibus
path_checker tur
path_selector "round-robin 0"
}
}
devices {
device {
vendor "iSCSI-Enterprise"
product "Virtual disk"
path_grouping_policy multibus
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
path_checker readsector0
path_selector "round-robin 0"
}
}
4、命令
[root@web2 ~]# multipath -h
multipath-tools v0.4.7 (03/12, 2006)
Usage: multipath [-v level] [-d] [-h|-l|-ll|-f|-F|-r]
[-p failover|multibus|group_by_serial|group_by_prio]
[device]
-v level verbosity level
0 no output
1 print created devmap names only
2 default verbosity
3 print debug information
-h print this usage text
-b file bindings file location
-d dry run, do not create or update devmaps
-l show multipath topology (sysfs and DM info)
-ll show multipath topology (maximum info)
-f flush a multipath device map
-F flush all multipath device maps
-r force devmap reload
-p policy force all maps to specified policy :
failover 1 path per priority group
multibus all paths in 1 priority group
group_by_serial 1 priority group per serial
group_by_prio 1 priority group per priority lvl
group_by_node_name 1 priority group per target node
device limit scope to the device's multipath
(udev-style $DEVNAME reference, eg /dev/sdb
or major:minor or a device map name)
[root@web2 ~]#
5、启动关闭
# /etc/init.d/multipathd start #开启mulitipath服务 service multipath start service multipath restart service multipath shutdown
6、如何获取wwid
1、 [root@vxfs01 ~]# cat /var/lib/multipath/bindings # Multipath bindings, Version : 1.0 # NOTE: this file is automatically maintained by the multipath program. # You should not need to edit this file in normal circumstances. # # Format: # alias wwid # mpath0 36006016051d50e0035744871c912de11 mpath1 36006016051d50e0034744871c912de11 mpath2 36006016051d50e0032744871c912de11 mpath3 36006016051d50e0039744871c912de11 mpath4 36006016051d50e003a744871c912de11 2、 [root@vxfs01 ~]# multipath -v3 |grep 3600 sdb: uid = 36006016051d50e003a744871c912de11 (callout) sdc: uid = 36006016051d50e003a744871c912de11 (callout) sdd: uid = 36006016051d50e003a744871c912de11 (callout) sde: uid = 36006016051d50e003a744871c912de11 (callout) 36006016051d50e003a744871c912de11 1:0:0:0 sdb 8:16 0 [undef][ready] DGC,RAI 36006016051d50e003a744871c912de11 1:0:1:0 sdc 8:32 1 [undef][ready] DGC,RAI 36006016051d50e003a744871c912de11 2:0:0:0 sdd 8:48 1 [undef][ready] DGC,RAI 36006016051d50e003a744871c912de11 2:0:1:0 sde 8:64 0 [undef][ready] DGC,RAI Found matching wwid [36006016051d50e003a744871c912de11] in bindings file.
比较详细的文字：
http://zhumeng8337797.blog.163.com/blog/static/1007689142013416111534352/
http://blog.csdn.net/wuweilong/article/details/14184097
RHEL官网资料：
http://www.prudentwoo.com/wp-content/uploads/downloads/2013/11/Red_Hat_Enterprise_Linux-5-DM_Multipath-en-US.pdf
http://www.prudentwoo.com/wp-content/uploads/downloads/2013/11/Red_Hat_Enterprise_Linux-5-DM_Multipath-zh-CN.pdf
http://www.prudentwoo.com/wp-content/uploads/downloads/2013/11/Red_Hat_Enterprise_Linux-6-DM_Multipath-en-US.pdf
http://www.prudentwoo.com/wp-content/uploads/downloads/2013/11/Red_Hat_Enterprise_Linux-6-DM_Multipath-zh-CN.pdf