系統環境：Centos 5
事項：Centos 5 創建軟件Raid 即 Mdadm用法
基本語法 ： mdadm [mode] <raid-device> [options] <component-devices>
mode 有7種：
Assemble：將以前定義的某個陣列加入當前在用陣列。
Build：Build a legacy array ，每個device 沒有 superblocks
Create：創建一個新的陣列，每個device 具有 superblocks
Manage： 管理陣列，比如 add 或 remove
Misc：允許單獨對陣列中的某個 device 做操作，比如抹去superblocks 或 終止在用的陣列。
Follow or Monitor:監控 raid 1,4,5,6 和 multipath 的狀態
Grow：改變raid 容量或 陣列中的 device 數目
可用的 [options]:
-A, --assemble：加入一個以前定義的陣列
-B, --build：Build a legacy array without superblocks.
-C, --create：創建一個新的陣列
-Q, --query：查看一個device，判斷它為一個 md device 或是 一個 md 陣列的一部分
-D, --detail：打印一個或多個 md device 的詳細信息
-E, --examine：打印 device 上的 md superblock 的內容
-F, --follow, --monitor：選擇 Monitor 模式
-G, --grow：改變在用陣列的大小或形態
-h, --help：幫助信息，用在以上選項后，則顯示該選項信息
--help-options
-V, --version
-v, --verbose：顯示細節
-b, --brief：較少的細節。用于 --detail 和 --examine 選項
-f, --force
-c, --config= ：指定配置文件，缺省為 /etc/mdadm .conf
-s, --scan：掃描配置文件或 /proc/mdstat以搜尋丟失的信息。
配置文件/etc/mdadm .conf
可以通過以下方式生成配置文件
mdadm -Ds >> /etc/mdadm.conf
mdadm .conf 格式：
DEVICE 所用到的設備分區列表（在mdadm 掃描時，將掃描這些分區）
ARRAY 定義實際的磁盤陣列
簡單實例：
DEVICE /dev/sda10 /dev/sda11 /dev/sdb10 /dev/sdb11
ARRAY /dev/md0 devices=/dev/sda11, /dev/sda10
1.實戰RAID
下面將通過實際操作，創建一個RAID1：
1．1 格式化待做軟RAID的分區：
準備兩個待做RAID1的分區/dev/sda10, /dev/sdb10：
要求： 大小近乎相等，格式為Linux raid autodetect （即：fd）；
# fdisk /dev/sda //使用fdisk創建分區
The number of cylinders for this disk is set to 9964.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): n //新建分區
Command action
l logical (5 or over)
p primary partition (1-4)
l
First cylinder (1012-9964, default 1012):
Using default value 1012
Last cylinder or +size or +sizeM or +sizeK (1012-1039, default 1012): 1025
Command (m for help): p //查看當前分區情況
Disk /dev/sda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 9964 80035798+ 5 Extended
/dev/sda5 917 927 88326 7 HPFS/NTFS
/dev/sda6 928 996 554211 b Win95 FAT32
/dev/sda7 997 1011 120456 7 HPFS/NTFS
/dev/sda8 1040 9964 71690031 83 Linux
/dev/sda9 1 916 7357707 83 Linux
/dev/sda10 1012 1025 112423+ 83 Linux
Partition table entries are not in disk order
Command (m for help): t //更改分區類型;
Partition number (1-10): 10
Hex code (type L to list codes): fd //設置分區類型為 Linux raid autodetect;
Command (m for help): w //保存退出;
# fdisk -l /dev/sda //查看驅動"/dev/sda"分區
Disk /dev/sda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 9964 80035798+ 5 Extended
/dev/sda5 917 927 88326 7 HPFS/NTFS
/dev/sda6 928 996 554211 b Win95 FAT32
/dev/sda7 997 1011 120456 7 HPFS/NTFS
/dev/sda8 1040 9964 71690031 83 Linux
/dev/sda9 1 916 7357707 83 Linux
/dev/sda10 1012 1025 112423+ fd Linux raid autodetect
Partition table entries are not in disk order
＃ fdisk -l /dev/sdb //同樣創建另一分區/dev/sdb10
Disk /dev/sdb: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb2 4501 9964 43889580 5 Extended
/dev/sdb3 667 4500 30796605 83 Linux
/dev/sdb4 658 666 72292+ 83 Linux
/dev/sdb5 5114 5362 2000061 83 Linux
/dev/sdb6 5751 5878 1028128+ 83 Linux
/dev/sdb7 5721 5750 240943+ 83 Linux
/dev/sdb8 5620 5720 811251 83 Linux
/dev/sdb9 6261 9964 29752348+ 83 Linux
/dev/sdb10 4501 4514 112423+ fd Linux raid autodetect
Partition table entries are not in disk order
創建RAID1
＃mdadm -C --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sda10 /dev/sdb10
＃或 mdadm -Cv /dev/md0 -l1 -n2 /dev/sda10 /dev/sdb10
mdadm : chunk size defaults to 64K
mdadm : /dev/sda10 appears to contain an ext2fs file system
size=112320K mtime=Sat Jan 1 06:39:59 2011
mdadm : /dev/sdb10 appears to be part of a raid array:
size=112320K ctime=Sat Jan 1 02:45:14 2011
Continue creating array? y
mdadm : array /dev/md0 started.
＃ mkfs.ext3 /dev/md0 //格式化raid分區類型為ext3
mke2fs 1.37 (21-Mar-2005)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
28112 inodes, 112320 blocks
5616 blocks (5.00%) reserved for the super user
First data block=1
14 block groups
8192 blocks per group, 8192 fragments per group
2008 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 23 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
# mdadm -D /dev/md0 //查看raid信息
/dev/md0:
Version : 00.90.01
Creation Time : Sat Jan 1 02:45:14 2011
Raid Level : raid1
Array Size : 112320 (109.71 MiB 115.02 MB)
Device Size : 112320 (109.71 MiB 115.02 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Sat Jan 1 05:08:27 2011
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : 797b80d8:4b70e2d1:7e427c7e:c9546d1b
Events : 0.10
Number Major Minor RaidDevice State
0 8 10 0 active sync /dev/sda10
1 8 26 1 active sync /dev/sdb10
# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda10[0] sdb10[1]
112320 blocks [2/2] [UU] raid autodetect
unused devices: <none>
＃ mount /dev/md0 /share/raid //掛載raid
＃ cp /share/partitionA2 /share/raid
＃ ls /share/raid
lost+found asdf.asf
netatalk.tar
# umount /share/raid
# mdadm /dev/md0 -r /dev/sda10 //將sda10從raid中移除
# mdadm -D /dev/md0
/dev/md0:
Version : 00.90.01
Creation Time : Sat Jan 1 02:45:14 2000
Raid Level : raid1
Array Size : 112320 (109.71 MiB 115.02 MB)
Device Size : 112320 (109.71 MiB 115.02 MB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Sat Jan 1 05:30:28 2000
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
UUID : 797b80d8:4b70e2d1:7e427c7e:c9546d1b
Events : 0.52
Number Major Minor RaidDevice State
0 0 0 0 removed
1 8 26 1 active sync /dev/sdb10
# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb10[1]
112320 blocks [2/1] [_U]
unused devices: <none>
將sda10的分區類型改為linux (即83)，然后重啟，重新掛載，查看分區里的文件：
# fdisk /dev/sda
t-->11 --> 83 --> w
# reboot
# mount /dev/sda10 /share/partition
# ls /share/partition
lost+found asdf.asf
netatalk.tar
和原來作為raid時的內容完全一樣，說明raid1 的確是在每個硬盤都寫入數據，有較高的可靠性。
1．3 數據恢復：
下面在sda上新建另一分區，sda11，并把它作為raid1的一個分區，即替代原來的sda10；
# mdadm /dev/md0 -a /dev/sda11
mdadm : hot added /dev/sda11
# mdadm -D /dev/md0
/dev/md0:
Version : 00.90.01
Creation Time : Sat Jan 1 02:45:14 2000
Raid Level : raid1
Array Size : 112320 (109.71 MiB 115.02 MB)
Device Size : 112320 (109.71 MiB 115.02 MB)
Raid Devices : 2
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Sat Jan 1 05:50:00 2000
State : clean
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
UUID : 797b80d8:4b70e2d1:7e427c7e:c9546d1b
Events : 0.111
Number Major Minor RaidDevice State
0 8 11 0 active sync /dev/sda11
1 8 26 1 active sync /dev/sdb10
# mount /dev/md0 /share/raid
# ls /share/raid
lost+found asdf.asf
netatalk.tar
1．4 其他操作：
# mdadm -S /dev/md0 （停止raid）
# mdadm -As /dev/md0 （根據mdadm .conf文件啟動raid）
# modprobe raid0.ko
# lsmod
raid0 5984 0 - Live 0xbf000000
# mdadm -C --verbose /dev/md0 -l0 -n2 /dev/sda11 /dev/sdb11 (raid0)
# modprobe xor.ko
# modprobe raid5.ko
# lsmod
Module Size Used by Not tainted
raid5 20544 0 - Live 0xbf006000
xor 5544 1 raid5, Live 0xbf003000
raid0 5984 0 - Live 0xbf000000
# mdadm -C --verbose /dev/md0 -l5 -n3 /dev/sda10 /dev/sda11 /dev/sdb11 (raid5)
常用命令：
mdadm -Cv /dev/md0 -l1 -n2 /dev/sdb7 /dev/sdb8 //創建Raid
mdadm -D /dev/md0 //查看Raid
mdadm -S /dev/md0 //停止Raid
mdadm -R /dev/md0 //
mdadm -As (－s指pg mdadm 的配置文件，如果沒有指定，則使用/etc/mdadm .conf
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