一步一步学习mdadm多路径

Step by step learning RedHat mdadm Multipathing

Deyou.Yang (yangdeyou@gmail.com) System Management.
15 May 2007

• 升级系统内核

#rpm -ivh mkinitrd-4.2.1.6-1.i386.rpm
#rpm -ivh kernel-smp-2.6.9-34.EL.i686.rpm
这个版本支持多路径比较稳定。

• 确定多路径通道

# scsi_id -g -p 0x80 -s /block/sda
SIBM 3542 1T05078453

# scsi_id -s -p 0x83 -s /block/sda
3600a0b80000b174b000000d63efc5c8c
# scsi_id -s -p 0x83 -s /block/sdc
3600a0b80000b174b000000d63efc5c8c

• 建立md设备

#mdadm -C /dev/md0 -l multipath -n2 /dev/sda /dev/sdc
显示/dev/md0设备信息
# mdadm -D /dev/md0
/dev/md1:
Version : 00.90.01
Creation Time : Tue Sep 19 13:55:26 2006
Raid Level : multipath
Array Size : 52428672 (49.100 GiB 53.69 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Tue Sep 19 13:55:26 2006
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0


Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sda
1 8 65 1 active sync /dev/sdc
UUID : 12748dca:832e7efe:95fcf673:8d88163f
Events : 0.1

• 设置重启自动建立md

#echo "DEVICE /dev/sd[a-z]*" > /etc/mdadm.conf
#mdadm -ES >> /etc/mdadm.conf
检查mdadm.conf文件，查看与mdamd -D /dev/md0的UUID是否相同。这里必需相同！
# cat /etc/mdadm.conf
DEVICE /dev/sd[1-z]*
ARRAY /dev/md0 level=multipath num-devices=2 UUID=a3e03ff7:179b59c3:9542fc5f:2249e151
devices=/dev/sda,/dev/sdc
如果要做A、B服务的raw的RAC，A、B可以看到相同的scsi id,在A机上做好md，把mdadm.conf传到B服务器上即可。

• 路径的恢复

# mdadm -D /dev/md0
/dev/md1:
Version : 00.90.01
Creation Time : Tue Sep 19 13:55:26 2006
Raid Level : multipath
Array Size : 52428672 (49.100 GiB 53.69 GB)
Raid Devices : 1
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Tue Sep 19 13:55:26 2006
State : clean
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1


Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sda
1 8 65 1 faulty /dev/sdc
UUID : 12748dca:832e7efe:95fcf673:8d88163f
Events : 0.1
mdamd /dev/md0 -f /dev/sdc -r /dev/sdc/ -a /dev/sdc

• 查看所有多路径的状态

# cat /proc/mdstat
Personalities : [multipath]
md1 : active multipath sda[1] sdc[0]
52428672 blocks [2/2] [UU]

unused devices:

注：可以在PC上用两个硬盘做md实验。文件系统要在md之后建立！