linux 自带的多路径

Linux自带多路径详解

　　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 } }<br><br>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.