mdadm指令詳解
mdadm指令詳解及實驗過程
線上學習影片分享：linux影片教學課程
一.概念
mdadm是multiple devices admin的簡稱，它是Linux下的一款標準的軟體RAID 管理工具，作者是Neil Brown
#二.特點
mdadm能夠診斷、監控和收集詳細的陣列資訊
mdadm是一個單獨整合化的程式而非一些分散程序的集合，因此對不同RAID管理指令有共通點的語法
mdadm能夠執行幾乎所有的功能而不需要配置文件(也沒有默認的配置文件）
三.作用（引用）
## 目前以MD(Multiple Devices)虛擬塊設備的方式實現軟體RAID,利用多個底層的區塊設備虛擬出一個新的虛擬設備,並且利用條帶化(stripping)技術將資料塊均勻分佈到多個磁碟上來提高虛擬設備的讀寫性能,利用不同的資料冗餘演算法來保護用戶資料不會因為某個塊設備的故障而完全丟失,而且還能在設備被替換後將丟失的數據恢復到新的設備上. 目前MD支援linear,multipath,raid0(stripping),raid1(mirror),raid4,raid5,raid6,raid10等不同的冗餘層級和層級方式,當然也能支援多個RAID陳列的層疊組成raid1 0,raid5 1等類型的陳列四.實驗 試題：建立4個大小為1G的磁盤，並將其中3個創建為raid5的陣列磁盤， 1個為熱備份磁碟。測試熱備份磁碟替換陣列中的磁碟並同步資料。移除損壞的磁碟，新增一個新磁碟作為熱備份磁碟。最後要求開機自動掛載。 4.1建立磁碟
[root@xiao ~]# 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
First cylinder (10486-13054, default 10486):
Using default value 10486
Last cylinder, +cylinders or +size{K,M,G} (10486-13054, default 13054): +1G
Command (m for help): n
First cylinder (10618-13054, default 10618):
Using default value 10618
Last cylinder, +cylinders or +size{K,M,G} (10618-13054, default 13054): +1G
Command (m for help): n
First cylinder (10750-13054, default 10750):
Using default value 10750
Last cylinder, +cylinders or +size{K,M,G} (10750-13054, default 13054): +1G
Command (m for help): n
First cylinder (10882-13054, default 10882):
Using default value 10882
Last cylinder, +cylinders or +size{K,M,G} (10882-13054, default 13054): +1G
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): 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): 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): 5
Hex code (type L to list codes): fd
Changed system type of partition 5 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sda: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 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: 0x0008ed57
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 204800 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 26 10225 81920000 83 Linux
/dev/sda3 10225 10486 2097152 82 Linux swap / Solaris
/dev/sda4 10486 13054 20633279 5 Extended
/dev/sda5 10486 10617 1058045 fd Linux raid autodetect
/dev/sda6 10618 10749 1060258+ fd Linux raid autodetect
/dev/sda7 10750 10881 1060258+ fd Linux raid autodetect
/dev/sda8 10882 11013 1060258+ 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.[root@xiao ~]# mdadm -C /dev/md0 -l 5 -n 3 -x 1 /dev/sda{5,6,7,8}
mdadm: /dev/sda5 appears to be part of a raid array:
level=raid5 devices=3 ctime=Wed Dec 17 00:58:24 2014
mdadm: /dev/sda6 appears to be part of a raid array:
level=raid5 devices=3 ctime=Wed Dec 17 00:58:24 2014
mdadm: /dev/sda7 appears to be part of a raid array:
level=raid5 devices=3 ctime=Wed Dec 17 00:58:24 2014
mdadm: /dev/sda8 appears to be part of a raid array:
level=raid5 devices=3 ctime=Wed Dec 17 00:58:24 2014
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.[root@xiao ~]# cat /proc/mdstat
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4]
md0 : active raid5 sda7[4] sda8[3](S) sda6[1] sda5[0]
2113536 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
[=========>...........] recovery = 45.5% (482048/1056768) finish=0.3min speed=30128K/sec
unused devices: <none>
[root@xiao ~]# cat /proc/mdstat
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4]
md0 : active raid5 sda7[4] sda8[3](S) sda6[1] sda5[0]
2113536 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
[root@xiao ~]# mke2fs -t ext3 /dev/md0 //格式化raid[root@xiao ~]# mount /dev/md0 /mnt [root@xiao ~]# ls /mnt lost+found
[root@xiao ~]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Dec 17 03:38:08 2014
Raid Level : raid5
Array Size : 2113536 (2.02 GiB 2.16 GB)
Used Dev Size : 1056768 (1032.17 MiB 1082.13 MB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed Dec 17 03:55:11 2014
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Name : xiao:0 (local to host xiao)
UUID : bce110f2:34f3fbf1:8de472ed:633a374f
Events : 18
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
1 8 6 1 active sync /dev/sda6
4 8 7 2 active sync /dev/sda7
3 8 8 - spare /dev/sda8[root@xiao ~]# mdadm /dev/md0 --fail /dev/sda6 mdadm: set /dev/sda6 faulty in /dev/md0
[root@xiao ~]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Dec 17 03:38:08 2014
Raid Level : raid5
Array Size : 2113536 (2.02 GiB 2.16 GB)
Used Dev Size : 1056768 (1032.17 MiB 1082.13 MB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed Dec 17 04:13:59 2014
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 3
Failed Devices : 1
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Rebuild Status : 43% complete
Name : xiao:0 (local to host xiao)
UUID : bce110f2:34f3fbf1:8de472ed:633a374f
Events : 26
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
3 8 8 1 spare rebuilding /dev/sda8
4 8 7 2 active sync /dev/sda7
1 8 6 - faulty /dev/sda6
[root@xiao ~]# cat /proc/mdstat
Personalities : [raid1] [raid0] [raid6] [raid5] [raid4]
md0 : active raid5 sda7[4] sda8[3] sda6[1](F) sda5[0]##4.8 移除損壞的硬碟
[root@xiao ~]# mdadm /dev/md0 -r /dev/sda6 mdadm: hot removed /dev/sda6 from /dev/md0
4.9新增一個新硬碟作為熱備份磁碟
[root@xiao ~]# 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
First cylinder (11014-13054, default 11014):
Using default value 11014
Last cylinder, +cylinders or +size{K,M,G} (11014-13054, default 13054): +1G
Command (m for help): t
Partition number (1-9): 9
Hex code (type L to list codes): fd
Changed system type of partition 9 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sda: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 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: 0x0008ed57
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 204800 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 26 10225 81920000 83 Linux
/dev/sda3 10225 10486 2097152 82 Linux swap / Solaris
/dev/sda4 10486 13054 20633279 5 Extended
/dev/sda5 10486 10617 1058045 fd Linux raid autodetect
/dev/sda6 10618 10749 1060258+ fd Linux raid autodetect
/dev/sda7 10750 10881 1060258+ fd Linux raid autodetect
/dev/sda8 10882 11013 1060258+ fd Linux raid autodetect
/dev/sda9 11014 11145 1060258+ 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.
[root@xiao ~]# partx -a /dev/sda9 /dev/sda
[root@xiao ~]# mdadm /dev/md0 --add /dev/sda9
mdadm: added /dev/sda9
[root@xiao ~]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Dec 17 03:38:08 2014
Raid Level : raid5
Array Size : 2113536 (2.02 GiB 2.16 GB)
Used Dev Size : 1056768 (1032.17 MiB 1082.13 MB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed Dec 17 04:39:35 2014
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Name : xiao:0 (local to host xiao)
UUID : bce110f2:34f3fbf1:8de472ed:633a374f
Events : 41
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
3 8 8 1 active sync /dev/sda8
4 8 7 2 active sync /dev/sda7
5 8 9 - spare /dev/sda95.開機自動掛載
#編輯/etc/ fsab檔案
/dev/md0 /mnt ext3 defaults 0 0
:wq
#
#6.mdadm中文man(引用)
基本語法： mdadm [mode] [options]
[mode] 有7種：
Assemble：將先前定義的某個陣列加入目前在用陣列。
Build：Build a legacy array ，每個device 沒有superblocks
Create：建立一個新的陣列，每個device 具有superblocks
Manage： 管理陣列，例如add或remove
Misc：允許單獨對陣列中的某個device 做操作，例如抹去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：加入一個先前定義的陣列
-B, --build：Build a legacy array without superblocks.
#-C, --create：建立一個新的陣列
-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：列印一個或多個md device 的詳細資訊
-E, --examine：列印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：幫助訊息，用在以上選項後，則顯示該選項訊息
--help-options
-V, --version
#-v, --verbose：顯示細節
#-b, -- brief：較少的細節。用於--detail 和--examine 選項
-f, --force
-c, --config= ：指定設定文件，缺省為/etc/mdadm/mdadm. conf
-s, --scan：掃描設定檔或/proc/mdstat以搜尋遺失的資訊。設定檔/etc/mdadm/mdadm.conf
create 或build 使用的選項:
-c, --chunk=:Specify chunk size of kibibytes. 預設為64.
--rounding=: Specify rounding factor for linear array (==chunk size)
-l, --level=:設定raid level.
#--create可用: linear, raid0, 0, stripe, raid1,1, mirror, raid4, 4, raid5, 5, raid6, 6, multipath, mp.
--build可用：linear, raid0, 0, stripe.
-p, --parity=：設定raid5 的奇偶校驗規則:eft-asymmetric, left-symmetric, right-asymmetric, right-symmetric, la, ra, ls, rs.缺省為left -symmetric
--layout=:類似於--parity
-n, --raid-devices=:指定陣列中可用device 數目，這個數目只能由--grow 修改
-x, --spare-devices=：指定初始陣列的富餘device 數目
-z, --size=：組成RAID1/4/5/6後從每個device取得的空間總數
--assume-clean:目前僅用於--build 選項
#-R, --run:陣列中的某一部分出現在其他陣列或檔案系統中時，mdadm會確認該陣列。此選項將不作確認。
-f, --force:通常mdadm不允許只用一個device 建立陣列，而且在建立raid5時會使用一個device作為missing drive。此選項正相反。
-a, --auto{=no,yes,md,mdp,part,p}{NN}：
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