极客笔记Linux mdadm命令：管理Linux软RAID。
Linux mdadm命令 功能描述
使用mdadm命令可以管理Linux软RAID，比如创建、调整、监控RAID。
- mdadm主要有以下8种使用模式。
- create：创建一个新的RAID，每个设备都具有元数据（超级块）。
- build：创建或组合一个没有元数据（超级块）的RAID。
- assemble：组装以前创建的RAID的组件集成到一个活动RAID。
- manage：更改一个现有的RAID，比如添加新的备用成员和删除故障设备。
- misc：报告或修改各种RAID相关设备，比如查询RAID或者设备的状态信息、删除旧的超级块。
- grow：调整/重新塑造一个活动RAID，比如改变RAID容量或阵列中的设备数目。
- monitor：监控一个或多个RAID的更改。
- incremental：添加设备到RAID中，或从RAID中删除设备。
Linux mdadm命令 语法
mdadm [模式] [ RAID设备] [选项] [RAID成员]
命令中各选项的含义如表所示。
备注：创建RAID准备工作–创建RAID分区。
在创建RAID设备之前，先要通过fdisk命令来创建RAID分区，创建方法和创建普通的磁盘分区类似，只不过在分区的时候将分区类型ID指定为fd。
使用以下命令创建磁盘分区/dev/sda5、/dev/sda6、/dev/sda7和/dev/sda8，每个磁盘分区大小为5GB，分区类型ID为fd。
[root@rhel ～]# fdisk /dev/sda
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command(m for help): n
//在此输入n，开始创建分区
Command action
e extended
p primary partition(1-4)
e
//在此输入e，开始创建扩展分区
Selected partition 4
First cylinder (19856-65270, default 19856):
//直接按回车键，从磁盘剩余起始柱面开始创建扩展分区
Using default value 19856
Last cylinder, +cylinders or +size{K, M, G} (19856-65270, default 65270):
//直接按回车键，则从第19856个柱面到最后一个柱面均为扩展分区
Using default value 65270
Command(m for help): n
First cylinder (19856-65270, default 19856):
//直接按回车键，从磁盘剩余起始柱面开始创建逻辑驱动器
Using default value 19856
Last cylinder, +cylinders or+size{K, M, G}(19856-65270, default 65270): +5G
//在此输入“+5G”，代表创建容量为5GB的逻辑驱动器
Command(m for help): n
First cylinder (20510-65270, default 20510):
Using default value 20510
Last cylinder, +cylinders or+size{K, M, G}(20510-65270, default 65270): +5G
Command(m for help): n
First cylinder (21164-65270, default 21164):
Using default value 21164
Last cylinder, +cylinders or+size{K, M, G}(21164-65270, default 65270): +5G
Command(m for help): n
First cylinder (21818-65270, default 21818):
Using default value 21818
Last cylinder, +cylinders or+size{K, M, G}(21818-65270, default 65270): +5G
Command(m for help): t
//在此输入t，开始转换分区类型
Partition number(1-8):5
//输入分区号码，在此输入5，说明要转换/dev/sda5分区的类型
Hex code(type L to list codes): fd
Changed system type of partition 5 to fd (Linux raid autodetect)
//转换5号分区类型为fd（Linux raid auto）
Command(m for help): t
Partition number(1-8):6
Hex code(type L to list codes): fd
Changed system type of partition 6 to fd (Linux raid autodetect)
Command(m for help): t
Partition number(1-8):7
Hex code(type L to list codes): fd
Changed system type of partition 7 to fd (Linux raid autodetect)
Command(m for help): t
Partition number(1-8):8
Hex code(type L to list codes): fd
Changed system type of partition 8 to fd (Linux raid autodetect)
Command(m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16： 设备或资源忙．
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
分区之后使用以下命令查看磁盘分区情况。
[root@rhel ～]# fdisk -l /dev/sda
Disk /dev/sda: 536.9 GB, 536870912000 bytes
255 heads, 63 sectors/track, 65270 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00034c36
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 102400 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 13 19595 157286400 83 Linux
/dev/sda3 19595 19856 2097152 82 Linux swap/Solaris
/dev/sda4 19856 65270 364794299 5 Extended
/dev/sda5 19856 20509 5251535 fd Linux raid autodetect
/dev/sda6 20510 21163 5253223+ fd Linux raid autodetect
/dev/sda7 21164 21817 5253223+ fd Linux raid autodetect
/dev/sda8 21818 22471 5253223+ fd Linux raid autodetect
//在此准备了4个磁盘分区做RAID 5实验
使用以下命令重新启动Linux系统。
[root@rhel ～]# init 6
Linux mdadm命令 示例
创建RAID 5设备，名称为/dev/md0，其成员为/dev/sda5、/dev/sda6和/dev/sda7
[root@rhel ～]# mdadm -C -v /dev/md0-l5-n3 /dev/sda5 /dev/sda6 /dev/sda7
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: size set to 5246976K
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
//RAID设备创建完成之后会立即启用
查看RAID设备/dev/md0详细信息
[root@rhel ～]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon Aug 19 01:02:312013
Raid Level : raid5
Array Size : 10493952 (10.01 GiB 10.75 GB)
Used Dev Size : 5246976 (5.00 GiB 5.37 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon Aug 19 01:10:332013
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name: rhel:0 (local to host rhel)
UUID : e7ed9356:a7d4e1ea:da5465ac:53f3dfe6
Events : 18
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
1 8 6 1 active sync /dev/sda6
3 8 7 2 active sync /dev/sda7
查看RAID成员/dev/sda5、/dev/sda6和/dev/sda7详细信息
[root@rhel ～]# mdadm -E /dev/sda5 /dev/sda6 /dev/sda7
/dev/sda5:
Magic: a92b4efc
Version:1.2
Feature Map:0x0
Array UUID: e7ed9356:a7d4e1ea:da5465ac:53f3dfe6
Name: rhel:0 (local to host rhel)
Creation Time: Mon Aug 19 01:02:312013
Raid Level: raid5
Raid Devices:3
Avail Dev Size:10494878(5.00 GiB 5.37 GB)
Array Size:10493952(10.01 GiB 10.75 GB)
Used Dev Size:10493952(5.00 GiB 5.37 GB)
Data Offset:8192 sectors
Super Offset:8 sectors
State: clean
Device UUID:57b31675:6484d43c:19a142a9:c40a5e1e
Update Time: Mon Aug 19 01:11:292013
Checksum:9003c6c-correct
Events:18
Layout: left-symmetric
Chunk Size:512K
Device Role: Active device 0
Array State: AAA('A'==active, '.'==missing)
/dev/sda6:
Magic: a92b4efc
Version:1.2
Feature Map:0x0
Array UUID: e7ed9356:a7d4e1ea:da5465ac:53f3dfe6
Name: rhel:0 (local to host rhel)
Creation Time: Mon Aug 19 01:02:312013
Raid Level: raid5
Raid Devices:3
Avail Dev Size:10498255(5.01 GiB 5.38 GB)
Array Size:10493952(10.01 GiB 10.75 GB)
Used Dev Size:10493952(5.00 GiB 5.37 GB)
Data Offset:8192 sectors
Super Offset:8 sectors
State: clean
Device UUID: cf95211c:93e66cd4:be5ab5bb:0021f0a0
Update Time: Mon Aug 19 01:11:292013
Checksum: dca85e26-correct
Events:18
Layout: left-symmetric
Chunk Size:512K
Device Role: Active device 1
Array State : AAA ('A' == active, '.' == missing)
/dev/sda7:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : e7ed9356:a7d4e1ea:da5465ac:53f3dfe6
Name: rhel:0 (local to host rhel)
Creation Time : Mon Aug 19 01:02:312013
Raid Level : raid5
Raid Devices : 3
Avail Dev Size:10498255(5.01 GiB 5.38 GB)
Array Size : 10493952 (10.01 GiB 10.75 GB)
Used Dev Size : 10493952 (5.00 GiB 5.37 GB)
Data Offset : 8192 sectors
Super Offset : 8 sectors
State : clean
Device UUID : ad9a8e7d:ee42d240:7cbd7057:254ad3a8
Update Time : Mon Aug 19 01:11:292013
Checksum : 4e194b44- correct
Events : 18
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 2
Array State : AAA ('A' == active, '.' == missing)
停用RAID设备/dev/md0
[root@rhel ～]# umount /dev/md0
//先卸载RAID设备文件系统
[root@rhel ～]# mdadm -S /dev/md0
mdadm: stopped /dev/md0
启用RAID设备/dev/md0
[root@rhel ～]# mdadm -A /dev/md0 /dev/sda5 /dev/sda6 /dev/sda7
mdadm: /dev/md0 has been started with 3 drives.
向RAID设备/dev/md0中添加备用成员/dev/sda8
[root@rhel ～]# mdadm /dev/md0-a /dev/sda8
mdadm: added /dev/sda8
将RAID设备/dev/md0中的备用成员转换为正式成员
[root@rhel ～]# mdadm -G /dev/md0-n4
mdadm: Need to backup 3072K of critical section..
将RAID成员/dev/sda7模拟为故障磁盘
[root@rhel ～]# mdadm -f /dev/md0 /dev/sda7
mdadm: set /dev/sda7 faulty in /dev/md0
热移除有故障的RAID成员/dev/sda7
[root@rhel ～]# mdadm -r /dev/md0 /dev/sda7
mdadm: hot removed /dev/sda7 from /dev/md0
删除RAID设备/dev/md0
[root@rhel ～]# umount /dev/md0
//卸载RAID设备文件系统[root@rhel ～]# mdadm -Ss /dev/md0
mdadm: stopped /dev/md0
//停用RAID设备
[root@rhel ～]# mdadm --zero-superblock /dev/sda5 /dev/sda6 /dev/sda7 /dev/sda8
//删除RAID设备
扩展RAID设备容量
[root@rhel ～]# mdadm -C /dev/md0-l5-n3 /dev/sda5 /dev/sda6 /dev/sda7-x1 /dev/sda8-z 4G
mdadm: /dev/sda5 appears to be part of a raid array:
level=raid5 devices=3 ctime=Sat Dec 7 16:14:272013
mdadm: /dev/sda6 appears to be part of a raid array:
level=raid5 devices=3 ctime=Sat Dec 7 16:14:272013
mdadm: /dev/sda7 appears to be part of a raid array:
level=raid5 devices=3 ctime=Sat Dec 7 16:14:272013
mdadm: largest drive (/dev/sda6) exceeds size (4194304K) by more than 1%
Continue creating array? y //输入y确认创建RAID设备
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
//创建RAID 5设备，正式成员为/dev/sda5、/dev/sda6和/dev/sda7，备用成员为/dev/sda8，每个RAID成员使用4GB容量（每个RAID成员总容量为5GB）
[root@rhel ～]# mdadm -G /dev/md0-z 5G
mdadm: component size of /dev/md0 has been set to 5242880K
//扩展RAID设备/dev/md0容量，每个RAID成员使用5GB容量