Linux 软RAID---mdadm
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一.RAID建立
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mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb{1,2}
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mdadm --create /dev/md0 --level=5 --raid-devices=2 /dev/sdb{1,2}
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添加热备:
mdadm --create /dev/md0 --add /dev/sdb3
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创建raid10
# mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb{1,2}
# mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdb{3,4}-a yes
# mdadm --create /dev/md2 --level=10 --raid-devices=2 /dev/md{0,1}-a yes
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二. /proc/mdstat
[root@station20~]# cat /proc/mdstat
Personalities: [raid1] [raid6] [raid5] [raid4]
md1: active raid5 sdb10[3] sdb9[1] sdb8[0]
????? 196224 blocks level 5, 64k chunk,algorithm 2 [3/2] [UU_]
????? [===============>.....]? recovery = 79.1% (78592/98112) finish=0.0minspeed=4136K/sec
?????
md0: active raid1 sdb7[1] sdb6[0]
????? 98112 blocks [2/2] [UU]
????? bitmap: 0/12 pages [0KB], 4KB chunk
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unuseddevices: <none>
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三.位图: --bitmap=internal
原理描述：
在mdadm操作中，bitmap用于记录RAID 阵列从上次同步之后更改的部分，即记录RAID阵列有多少个块已经同步(resync)。RAID 阵列会定期将信息写入到bitmap 中。在一般情况下，磁盘阵列在重启之后会有一个完整的同步过程。如果有bitmap，那么只有被修改后的数据才会被同步。在另一种情况下，如果阵列一块磁盘被取出，bitmap不会被清除，当这块磁盘重新加入阵列时，同样只会同步改变过的数据。所以bitmap能够减少磁盘阵列同步的时间，起到优化raid1的作用。Bitmap一般写入的位置是磁盘的metadata或者我们成为外部的另外，要注意的是，bitmap只是对raid1的功能，对raid0等其他设备来说是没有意义的.
注意: 此功能只对RAID1有效
Example: mdadm --create /dev/md0 --level=1 --raid-devices=2 -a yes-b internal
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在已存在的RAID1上启用视图
mdadm --grow /dev/md0 --bitmap=internal
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四. 共享热备盘及邮件通知
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[root@server109~]# mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda{5,6} -a yes -binternal
[root@server109~]# mdadm --create /dev/md1 --level=5 --raid-devices=3 /dev/sda{7,8,9} -a yes
[root@server109~]# mdadm /dev/md0 --add /dev/sda10
[root@server109~]# cat /proc/mdstat
Personalities: [raid1] [raid6] [raid5] [raid4]
md1: active raid5 sda9[2] sda8[1] sda7[0]
????? 196736 blocks level 5, 64k chunk,algorithm 2 [3/3] [UUU]
?????
md0: active raid1 sda10[2](S) sda6[1] sda5[0]
????? 98368 blocks [2/2] [UU]
????? bitmap: 0/13 pages [0KB], 4KB chunk
unuseddevices: <none>
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[root@server109~]# mdadm --examine --scan > /etc/mdadm.conf
[root@server109~]# cat /etc/mdadm.conf
ARRAY/dev/md1 level=raid5 num-devices=3 UUID=891d6352:a0a4efff:4f162d90:c3500453
ARRAY/dev/md0 level=raid1 num-devices=2 UUID=b070e059:fe2cf975:aac92394:e103a46d
?? spares=1
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可以实现热备共享及邮件通知的配置文件如下(直接修改mdadm.conf):
[root@server109~]# cat /etc/mdadm.conf
##Share Host Spares
ARRAY/dev/md1 level=raid5 num-devices=3 UUID=891d6352:a0a4efff:4f162d90:c3500453spare-group=1
ARRAY/dev/md0 level=raid1 num-devices=2 UUID=b070e059:fe2cf975:aac92394:e103a46dspare-group=1
?? spares=1
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##Mail Notification
MAILFROM root@localhost??????????? ## 邮件发出,不写默认为root
MAILADDR raider@localhost??????##邮件接收
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[root@server109~]# /etc/init.d/mdmonitor start
[root@server109~]# useradd raider
[root@server109~]# echo redhat | passwd --stdin raider
[root@server109~]# cat /proc/mdstat
Personalities: [raid1] [raid6] [raid5] [raid4]
md1: active raid5 sda9[2] sda8[1] sda7[0]
????? 196736 blocks level 5, 64k chunk,algorithm 2 [3/3] [UUU]
?????
md0: active raid1 sda10[2](S) sda6[1] sda5[0]
????? 98368 blocks [2/2] [UU]
????? bitmap: 0/13 pages [0KB], 4KB chunk
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unuseddevices: <none>
[root@server109~]# mdadm /dev/md1 -f /dev/sda7 -r /dev/sda7
mdadm:set /dev/sda7 faulty in /dev/md1
mdadm:hot removed /dev/sda7
[root@server109~]# cat /proc/mdstat
Personalities: [raid1] [raid6] [raid5] [raid4]
md1: active raid5 sda10[3] sda9[2] sda8[1]
????? 196736 blocks level 5, 64k chunk,algorithm 2 [3/2] [_UU]
????? [====>................]? recovery = 24.7% (25472/98368) finish=0.1minspeed=6368K/sec
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md0: active raid1 sda6[1] sda5[0]
????? 98368 blocks [2/2] [UU]
????? bitmap: 0/13 pages [0KB], 4KB chunk
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[root@server109~]# mail -u raider
Mailversion 8.1 6/6/93.? Type ? for help.
"/var/mail/raider":1 message 1 new
>N? 1 root@server109.examp? Tue Jan?4 04:28? 35/1262? "Fail event on/dev/md1:server109.example.com"
&1
Message1:
Fromroot@server109.example.com? Tue Jan? 4 04:28:48 2011
Date:Tue, 4 Jan 2011 04:28:47 +0100
From:root@server109.example.com
To:raider@server109.example.com
Subject:Fail event on /dev/md1:server109.example.com
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.........................
AFail event had been detected on md device /dev/md1.
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Itcould be related to component device /dev/sda7.
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...............................
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五.RAID扩展 --grow
如果某天RAID 空间不够用了,如何增加RAID的空间呢?
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Thesteps for adding a new disk are:
1. Add the new disk to the active 3-device RAIDS (starts as a spare):
mdadm -add /dev/mdO/dev/hda8
2 Reshape the RAID5:
mdadm --grow /dev/md0 --raid-devices=4
3. Monitor the reshaping process and estimated time to finish:
watch -n 1 'cat/proc/mdstat'
4.Expand the FS to fill the new space:
resize2fs /dev/md0
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[root@server109 ~]# mdadm /dev/md1 --add /dev/sda11
[root@server109 ~]# mdadm /dev/md1 --grow --raid-devices=5
[root@server109~]# cat /proc/mdstat
Personalities: [raid1] [raid6] [raid5] [raid4]
md1: active raid5 sda11[4] sda7[3] sda10[0] sda9[2] sda8[1]
????? 295104 blocks super 0.91 level 5, 64kchunk, algorithm 2 [5/5] [UUUUU]
????? [>....................]? reshape =?2.0% (2812/98368) finish=1.0min speed=1406K/sec
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md0: active raid1 sda6[1] sda5[0]
????? 98368 blocks [2/2] [UU]
????? bitmap: 0/13 pages [0KB], 4KB chunk
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unuseddevices: <none>
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[root@server109~]# resize2fs /dev/md1
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六. RAID 恢复
OS为独立硬盘,数据存储在一个RAID5 上,重新安装OS后如何恢复RAID呢?
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[root@server109~]# mdadm --examine /dev/sda8
/dev/sda8:
????????? Magic : a92b4efc
??????? Version : 0.90.00
?????????? UUID :891d6352:a0a4efff:4f162d90:c3500453
? Creation Time : Tue Jan? 4 04:18:45 2011
???? Raid Level : raid5
? Used Dev Size : 98368 (96.08 MiB 100.73 MB)
???? Array Size : 393472 (384.31 MiB 402.92 MB)
?? Raid Devices : 5
? Total Devices : 5
PreferredMinor : 1
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??? Update Time : Tue Jan? 4 05:17:52 2011
????????? State : clean
?Active Devices : 5
WorkingDevices : 5
?Failed Devices : 0
? Spare Devices : 0
?????? Checksum : 7f9b882a - correct
???????? Events : 206
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???????? Layout : left-symmetric
???? Chunk Size : 64K
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????? Number??Major?? Minor?? RaidDevice State
this???? 1??????8??????? 8??????? 1?????active sync?? /dev/sda8
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?? 0????0?????? 8?????? 10???????0????? active sync?? /dev/sda10
?? 1????1?????? 8??????? 8???????1????? active sync?? /dev/sda8
?? 2????2?????? 8??????? 9???????2????? active sync?? /dev/sda9
?? 3????3?????? 8??????? 7???????3????? active sync?? /dev/sda7
?? 4????4?????? 8?????? 11???????4????? active sync?? /dev/sda11
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[root@server109~]# mdadm -A /dev/md1 /dev/sda{7,8,9,10,11}
mdadm:/dev/md1 has been started with 5 drives.
[root@server109~]# mount /dev/md1 /mnt/
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七.Raid 重命名
rename /dev/md1 to /dev /md3
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[root@server109~]# umount /mnt/
[root@server109~]# mdadm --stop /dev/md1
[root@server109~]# mdadm --assemble /dev/md3 --super-minor=1 --update=super-minor/dev/sda{7,8,9,10,11}
说明: --super-minor=1? 这里的"1"与/dev/md1一至,如果重命令的是/dev/md0,那这里就是--super-minor=0
