一、多路徑解釋 多路徑，顧名思義就是有多種選擇的路徑。在SAN或IPSAN環境，主機和存儲之間外加了光纖交換機，這就導致主機和存儲之間交換速度和效率增強，一條路徑肯定是不行的，也是不安全不穩定的。多路徑就是要來解決從主機到磁盤之間最快，最高效的問題。主要實現如下幾個功能
故障的切換和恢復
IO流量的負載均衡
磁盤的虛擬化
多路徑之前一直是存儲廠商負責解決，竟來被拆分出來單獨賣錢了。
構架基本是這樣的：存儲，多路徑軟件，光纖交換機，主機，主機系統。
二、LINUX下的multipath
1、查看是否自帶安裝？
[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、安裝
rpm -ivh device-mapper-1.02.39-1.el5.rpm #安裝映射包
rpm -ivh device-mapper-multipath-0.4.7-34.el5.rpm #安裝多路徑包
外加加入開機啟動
chkconfig –level 2345 multipathd on #設置成開機自啟動multipathd
lsmod |grep dm_multipath #來檢查安裝是否正常
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" } } |
[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、啟動關閉
# /etc/init.d/multipathd start #開啟mulitipath服務
service multipath start
service multipath restart
service multipath shutdown
6、如何獲取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.