1 什么是raid
raid全稱是獨立磁盤冗余陣列（redundant array of independent disks），基本思想是把多個磁盤組合起來，組合一個磁盤陣列組，使得性能大幅提高。
raid分為幾個不同的等級，各個不同的等級均在數據可靠性及讀寫性能做了不同的權衡。實際工作中根據自己的業務需求選擇不同的raid方案。
2 raid的實現方式
外接式磁盤陣列：通過擴展卡提供適配能力內接式raid：主板集成raid控制器安裝os前在bios里配置軟件raid：通過os實現
3 標準的raid
3.1 raid0
raid0稱為條帶化存儲，將數據分段存儲在各個磁盤中，讀寫均可以并行處理，因此讀寫速率為單個磁盤的n倍，沒有冗余功能，任何一個磁盤的損壞就會導致的數據不可用。
3.2 raid1
radi1是鏡像存儲，沒有數據校驗，數據被同等的寫入到2個或者多個磁盤中，寫入速度相對慢， 但是讀取速度比較快。
3.3 raid 4
radi4在raid1的基礎上，n個盤用于數據存儲，另外加入了1個磁盤作為校驗盤。一共n+1個盤，任何一個盤壞掉也不影響數據的訪問
3.4 raid 5
raid5在raid4的基礎上，由原來的一個盤來存儲校驗數據，改為每個盤都有數據和校驗信息的。
4 混合raid
4.1 raid01
先組成raid0,然后組成raid1.
4.2 raid10
先組成raid1,然后組成raid0
5 軟raid的實現
5.1 raid5的實現
創建由三塊硬盤組成的可用空間為2g的raid5設備，要求其chunk大小為256k，文件系統為ext4，開機可自動掛載至/mydata目錄
5.1.1 先看看我們的磁盤情況
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[root@centos7 bash]$ lsblkname maj:min rm size ro type mountpointsda 8:0 0 200g 0 disk ├─sda1 8:1 0 1g 0 part /boot├─sda2 8:2 0 128g 0 part ├─sda3 8:3 0 48.8g 0 part /├─sda4 8:4 0 512b 0 part └─sda5 8:5 0 19.5g 0 part /appsdb 8:16 0 100g 0 disk sdc 8:32 0 20g 0 disk sdd 8:48 0 20g 0 disk sde 8:64 0 20g 0 disk sdf 8:80 0 20g 0 disk sr0 11:0 1 8.1g 0 rom /run/media/root/centos 7 x86_64 |
這里我們使用sdb,sdc,sdd,每個盤創建一個主分區1g,構建radi5.
5.1.2 根據實際情況分區
[root@centos7 bash]$ fdisk /dev/sdb
welcome to fdisk (util-linux 2.23.2).
changes will remain in memory only, until you decide to write them.
be careful before using the write command.
device does not contain a recognized partition table
building a new dos disklabel with disk identifier 0x93d380cf.
command (m for help): n
partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
select (default p): p
partition number (1-4, default 1):
first sector (2048-209715199, default 2048):
using default value 2048
last sector, +sectors or +size{k,m,g} (2048-209715199, default 209715199): +1g
partition 1 of type linux and of size 1 gib is set
command (m for help): t
selected partition 1
hex code (type l to list all codes): fd
changed type of partition 'linux' to 'linux raid autodetect'
command (m for help): p
disk /dev/sdb: 107.4 gb, 107374182400 bytes, 209715200 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk label type: dos
disk identifier: 0x93d380cf
device boot start end blocks id system
/dev/sdb1 2048 2099199 1048576 fd linux raid autodetect
command (m for help): w
the partition table has been altered!
calling ioctl() to re-read partition table.
syncing disks.
[root@centos7 bash]$ fdisk /dev/sdc
welcome to fdisk (util-linux 2.23.2).
changes will remain in memory only, until you decide to write them.
be careful before using the write command.
device does not contain a recognized partition table
building a new dos disklabel with disk identifier 0xc56b90d8.
command (m for help): n
partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
select (default p): p
partition number (1-4, default 1):
first sector (2048-41943039, default 2048):
using default value 2048
last sector, +sectors or +size{k,m,g} (2048-41943039, default 41943039): +1g
partition 1 of type linux and of size 1 gib is set
command (m for help): t
selected partition 1
hex code (type l to list all codes): fd
changed type of partition 'linux' to 'linux raid autodetect'
command (m for help): p
disk /dev/sdc: 21.5 gb, 21474836480 bytes, 41943040 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk label type: dos
disk identifier: 0xc56b90d8
device boot start end blocks id system
/dev/sdc1 2048 2099199 1048576 fd linux raid autodetect
command (m for help): w
the partition table has been altered!
calling ioctl() to re-read partition table.
syncing disks.
[root@centos7 bash]$ fdisk /dev/sdd
welcome to fdisk (util-linux 2.23.2).
changes will remain in memory only, until you decide to write them.
be careful before using the write command.
device does not contain a recognized partition table
building a new dos disklabel with disk identifier 0x7e0900d8.
command (m for help): n
partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
select (default p): p
partition number (1-4, default 1):
first sector (2048-41943039, default 2048):
using default value 2048
last sector, +sectors or +size{k,m,g} (2048-41943039, default 41943039): +1g
partition 1 of type linux and of size 1 gib is set
command (m for help): p
disk /dev/sdd: 21.5 gb, 21474836480 bytes, 41943040 sectors
units = sectors of 1 * 512 = 512 bytes
sector size (logical/physical): 512 bytes / 512 bytes
i/o size (minimum/optimal): 512 bytes / 512 bytes
disk label type: dos
disk identifier: 0x7e0900d8
device boot start end blocks id system
/dev/sdd1 2048 2099199 1048576 83 linux
command (m for help): t
selected partition 1
hex code (type l to list all codes): fd
changed type of partition 'linux' to 'linux raid autodetect'
command (m for help): w
the partition table has been altered!
calling ioctl() to re-read partition table.
syncing disks.
5.1.3 創建raid
[root@centos7 bash]$ mdadm -c /dev/md5 -a yes -l 5 -n 3 /dev/sd{b1,c1,d1} -c 256 # -c指定創建， -a yes 自動創建設備 ， -l 設定level , -n 設定磁盤個數， -c chunk大小
continue creating array? y
mdadm: defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.
[root@centos7 bash]$ mdadm -ds # 查看信息
array /dev/md5 metadata=1.2 name=centos7.magedu.com:5 uuid=2c8ae60d:a799fcb7:9008a046:ae6ea430
[root@centos7 bash]$ mdadm -ds >/etc/mdadm.conf # 將軟raid信息寫入到配置文件中去
[root@centos7 bash]$ mkdir /mnt/md5 # 創建掛載點目錄
[root@centos7 bash]$ mkfs.ext4 /dev/md5 # 創建文件系統
mke2fs 1.42.9 (28-dec-2013)
filesystem label=
os type: linux
block size=4096 (log=2)
fragment size=4096 (log=2)
stride=64 blocks, stripe width=128 blocks
131072 inodes, 523776 blocks
26188 blocks (5.00%) reserved for the super user
first data block=0
maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
allocating group tables: done
writing inode tables: done
creating journal (8192 blocks): done
writing superblocks and filesystem accounting information: done
[root@centos7 bash]$ mount /dev/md5 /mnt/md5 # 掛載設備
[root@centos7 bash]$ tail -n 1 /etc/mtab
/dev/md5 /mnt/md5 ext4 rw,seclabel,relatime,stripe=128,data=ordered 0 0 # 查看掛載信息
[root@centos7 bash]$ tail -n 1 /etc/mtab >>/etc/fstab #添加到fstab文件中，確保開機啟動，這里建議使用uuid
5.1.4 驗證raid
[root@centos7 md5]$ mdadm -d /dev/md5 #查看詳細raid5詳細信息，可以發現有3個都是working狀態的 /dev/md5: version : 1.2 creation time : wed dec 6 19:28:22 2017 raid level : raid5 array size : 2095104 (2046.00 mib 2145.39 mb) used dev size : 1047552 (1023.00 mib 1072.69 mb) raid devices : 3 total devices : 3 persistence : superblock is persistent update time : wed dec 6 19:39:06 2017 state : clean active devices : 3 working devices : 3 failed devices : 0 spare devices : 0 layout : left-symmetric chunk size : 256k consistency policy : resync name : centos7.magedu.com:5 (local to host centos7.magedu.com) uuid : 2c8ae60d:a799fcb7:9008a046:ae6ea430 events : 18 number major minor raiddevice state 0 8 17 0 active sync /dev/sdb1 1 8 33 1 active sync /dev/sdc1 3 8 49 2 active sync /dev/sdd1 [root@centos7 md5]$ man mdadm [root@centos7 md5]$ mdadm /dev/md5 -f /dev/sdc1 # -f 設定指定設備故障， 將/dev/sdc1 這個盤標記失敗， 看是否數據能訪問，我這里使用-f標記失敗，工作中可以根據硬盤指示燈判斷磁盤狀態 mdadm: set /dev/sdc1 faulty in /dev/md5 [root@centos7 md5]$ mdadm -d /dev/md5 #在次查看信息，發現工作的是2個， 一個失敗的設備 /dev/md5: version : 1.2 creation time : wed dec 6 19:28:22 2017 raid level : raid5 array size : 2095104 (2046.00 mib 2145.39 mb) used dev size : 1047552 (1023.00 mib 1072.69 mb) raid devices : 3 total devices : 3 persistence : superblock is persistent update time : wed dec 6 19:41:08 2017 state : clean, degraded # 這里注意了。 我們的一個盤壞掉了。 raid5狀態為降級使用了。 active devices : 2 working devices : 2 failed devices : 1 spare devices : 0 layout : left-symmetric chunk size : 256k consistency policy : resync name : centos7.magedu.com:5 (local to host centos7.magedu.com) uuid : 2c8ae60d:a799fcb7:9008a046:ae6ea430 events : 20 number major minor raiddevice state 0 8 17 0 active sync /dev/sdb1 - 0 0 1 removed 3 8 49 2 active sync /dev/sdd1 1 8 33 - faulty /dev/sdc1 [root@centos7 md5]$ cat a.txt # 發現我們的數據還是能訪問的。沒有問題。
5.1.5 替換設備
我這里是磁盤壞掉后的執行替換的， 完全可以多一個備用盤， 壞掉自動替換的。
[root@centos7 md5]$ mdadm /dev/md5 -a /dev/sde1 # 上面我們的sdc1數據損壞，我們需要更換新的磁盤來頂替他的位置。這里添加一個sde1的磁盤， fdisk操作這里省去了。 mdadm: added /dev/sde1 [root@centos7 md5]$ mdadm -ds # 查看詳細信息 array /dev/md5 metadata=1.2 name=centos7.magedu.com:5 uuid=2c8ae60d:a799fcb7:9008a046:ae6ea430 [root@centos7 md5]$ mdadm -d /dev/md5 # 查看詳細信息 /dev/md5: version : 1.2 creation time : wed dec 6 19:28:22 2017 raid level : raid5 array size : 2095104 (2046.00 mib 2145.39 mb) used dev size : 1047552 (1023.00 mib 1072.69 mb) raid devices : 3 total devices : 4 persistence : superblock is persistent update time : wed dec 6 19:50:01 2017 state : clean # 狀態恢復正常了。沒有問題 active devices : 3 working devices : 3 failed devices : 1 spare devices : 0 layout : left-symmetric chunk size : 256k consistency policy : resync name : centos7.magedu.com:5 (local to host centos7.magedu.com) uuid : 2c8ae60d:a799fcb7:9008a046:ae6ea430 events : 43 number major minor raiddevice state 0 8 17 0 active sync /dev/sdb1 4 8 65 1 active sync /dev/sde1 3 8 49 2 active sync /dev/sdd1 1 8 33 - faulty /dev/sdc1 # 這個盤是壞掉的，我們已經加入了新的磁盤， 這個盤可以干掉了 [root@centos7 md5]$ man mdadm [root@centos7 md5]$ mdadm /dev/md5 --remove /dev/sdc1 # 這個盤我們從raid5中移除去。 mdadm: hot removed /dev/sdc1 from /dev/md5
5.1.6擴展raid
我們上面使用的是2+1構成的raid5,磁盤利用率為66%，如果我們想改成3+1 可以執行類似如下命令
[root@centos7 mnt]$ mkadm -g -r /dev/md5 -n 4 -a /dev/sdxx # 這里我就不測試了。使用/dev/sdxx代替一個設備。-g 是grown增長的意思，-r 是resizefs的意思，
5.1.7 清空raid信息
[root@centos7 mnt]$ umount /dev/md5 # 卸載設備 [root@centos7 mnt]$ mdadm -s /dev/md5 # 停止raid5 mdadm: stopped /dev/md5 [root@centos7 mnt]$ sed -i '$d' /etc/fstab # 刪除fstab中關于raid5掛載的行 [root@centos7 mnt]$ cat /etc/fstab # 確保fstab沒有大問題 # # /etc/fstab # created by anaconda on tue nov 7 16:07:01 2017 # # accessible filesystems, by reference, are maintained under '/dev/disk' # see man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # uuid=59ccea87-3c4e-4bbc-9e2f-3fadb1dcf2e6 / ext4 defaults 1 1 uuid=f4e867e8-bcde-43a2-adc7-c80b0948e85f /app ext4 noatime,usrquota,grpquota 1 2 uuid=1d6cbe88-ffb4-4adf-bacf-76be1fa75708 /boot ext4 defaults 1 2 #uuid=b2c064f5-1ee5-4b5c-9e75-ed41cb99c5aa swap swap defaults 0 0 #uuid=a0516c4f-40e6-4919-905a-8b44db12ff7b swap swap defaults,pri=0 0 0 #/dev/sdb2 /test ext4 rw,seclabel,relatime,data=ordered 0 0 #/dev/sdb1 /home xfs rw,seclabel,relatime,attr2,inode64,usrquota,grpquota 0 0 [root@centos7 mnt]$ rm -rf /etc/mdadm.conf # 刪除raid默認配置文件
[root@centos7 mnt]$ mdadm --zero-superblock /dev/sd{b1,e1,d1,c1} # 清空設置上的超級塊信息
5.2 raid10的實現
raid10 ，6個分區，2個一組raid1,3組raid0
5.2.1 案例分析
分析下，我們創建一個raid10設置，2個設備組成一個raid1,6個設備2個一組可以組成3個raid1, 然后把3個raid1組成一個raid0即可
5.2.2 先創建6個設備
[root@centos7 mnt]$ lsblk # 就是使用fdisk 創建的設備， 具體這里就不寫了。 最終使用lsblk顯示，我們可以看到sdb1,sdb2,sdd1,sde1一共6個磁盤 name maj:min rm size ro type mountpoint sda 8:0 0 200g 0 disk ├─sda1 8:1 0 1g 0 part /boot ├─sda2 8:2 0 128g 0 part ├─sda3 8:3 0 48.8g 0 part / ├─sda4 8:4 0 512b 0 part └─sda5 8:5 0 19.5g 0 part /app sdb 8:16 0 100g 0 disk ├─sdb1 8:17 0 1g 0 part └─sdb2 8:18 0 1g 0 part sdc 8:32 0 20g 0 disk ├─sdc1 8:33 0 1g 0 part └─sdc2 8:34 0 1g 0 part sdd 8:48 0 20g 0 disk └─sdd1 8:49 0 1g 0 part sde 8:64 0 20g 0 disk └─sde1 8:65 0 1g 0 part sdf 8:80 0 20g 0 disk sr0 11:0 1 8.1g 0 rom /run/media/root/centos 7 x86_64
5.2.3 創建raid
[root@centos7 mnt]$ mdadm -c /dev/md11 -a yes -l 1 -n 2 /dev/sd{b1,c1} # 創建第一個raid1
mdadm: /dev/sdb1 appears to be part of a raid array:
level=raid5 devices=3 ctime=wed dec 6 19:28:22 2017
mdadm: note: this array has metadata at the start and
may not be suitable as a boot device. if you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
mdadm: /dev/sdc1 appears to be part of a raid array:
level=raid5 devices=3 ctime=wed dec 6 19:28:22 2017
continue creating array? y
mdadm: defaulting to version 1.2 metadata
mdadm: array /dev/md11 started.
[root@centos7 mnt]$ mdadm -c /dev/md12 -a yes -l 1 -n 2 /dev/sd{b2,c2} #創建第二個raid1
mdadm: note: this array has metadata at the start and
may not be suitable as a boot device. if you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
continue creating array? y
mdadm: defaulting to version 1.2 metadata
mdadm: array /dev/md12 started.
[root@centos7 mnt]$ mdadm -c /dev/md13 -a yes -l 1 -n 2 /dev/sd{d1,e1} # 創建第三個raid1
mdadm: /dev/sdd1 appears to be part of a raid array:
level=raid5 devices=3 ctime=wed dec 6 19:28:22 2017
mdadm: note: this array has metadata at the start and
may not be suitable as a boot device. if you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
mdadm: /dev/sde1 appears to be part of a raid array:
level=raid5 devices=3 ctime=wed dec 6 19:28:22 2017
continue creating array? y
mdadm: defaulting to version 1.2 metadata
mdadm: array /dev/md13 started.
[root@centos7 mnt]$ mdadm -c /dev/md10 -a yes -l 0 -n 3 /dev/md{11,12,13} # 將3個raid1 合并為一個raid0
mdadm: /dev/md11 appears to contain an ext2fs file system
size=2095104k mtime=wed dec 6 19:29:45 2017
mdadm: /dev/md13 appears to contain an ext2fs file system
size=2095104k mtime=wed dec 6 19:29:45 2017
continue creating array? y
mdadm: defaulting to version 1.2 metadata
mdadm: array /dev/md10 started.
[root@centos7 mnt]$ mkfs.ext
mkfs.ext2 mkfs.ext3 mkfs.ext4
[root@centos7 mnt]$ mkfs.ext4 /dev/md10 # 創建文件系統
mke2fs 1.42.9 (28-dec-2013)
filesystem label=
os type: linux
block size=4096 (log=2)
fragment size=4096 (log=2)
stride=128 blocks, stripe width=384 blocks
196224 inodes, 784896 blocks
39244 blocks (5.00%) reserved for the super user
first data block=0
maximum filesystem blocks=805306368
24 block groups
32768 blocks per group, 32768 fragments per group
8176 inodes per group
superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
allocating group tables: done
writing inode tables: done
creating journal (16384 blocks): done
writing superblocks and filesystem accounting information: done
[root@centos7 mnt]$ mdadm -ds # 查看配置信息
array /dev/md11 metadata=1.2 name=centos7.magedu.com:11 uuid=0ce2cd6c:cd21fab6:3e65cfb5:64bd86f3
array /dev/md12 metadata=1.2 name=centos7.magedu.com:12 uuid=8af31dff:efab06ed:48e2613b:a599c774
array /dev/md13 metadata=1.2 name=centos7.magedu.com:13 uuid=a8c99d60:2d0c61e7:97a76809:9396c020
array /dev/md10 metadata=1.2 name=centos7.magedu.com:10 uuid=50b2fa58:4ce65d67:8c50c853:fa175a28
[root@centos7 mnt]$ mdadm -ds >> /etc/mdadm.conf # 寫配置文件到mdadm的配置文件中
[root@centos7 mnt]$ mkdir /mnt/md10 # 創建掛載目錄
[root@centos7 mnt]$ mount /dev/md10 /mnt/md10 # 掛載文件系統
[root@centos7 mnt]$ tail -n 1 /etc/mtab # 查看mtab文件中的最后一行， 也就是我們的md10掛載信息
/dev/md10 /mnt/md10 ext4 rw,seclabel,relatime,stripe=384,data=ordered 0 0
[root@centos7 mnt]$ tail -n 1 /etc/mtab >> /etc/fstab #添加到開機啟動
5.2.4 raid 清除工作
[root@centos7 mnt]$ umount /dev/md10 # 取消掛載
[root@centos7 mnt]$ rm -rf /etc/mdadm.conf # 刪除mdadm的默認配置
[root@centos7 mnt]$ mdadm -s /dev/md10 # 停止raid0設置
mdadm: stopped /dev/md10
[root@centos7 mnt]$ mdadm -s /dev/md11 # 停止raid1設置
mdadm: stopped /dev/md11
[root@centos7 mnt]$ mdadm -s /dev/md12 # 停止radi1 設置
mdadm: stopped /dev/md12
[root@centos7 mnt]$ mdadm -s /dev/md13 # 停止raid 1 設置
mdadm: stopped /dev/md13
[root@centos7 mnt]$ sed -i '$d' /etc/fstab # 刪除fstab的掛載
[root@centos7 mnt]$ cat /etc/fstab # 確保正確
#
# /etc/fstab
# created by anaconda on tue nov 7 16:07:01 2017
#
# accessible filesystems, by reference, are maintained under '/dev/disk'
# see man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
uuid=59ccea87-3c4e-4bbc-9e2f-3fadb1dcf2e6 / ext4 defaults 1 1
uuid=f4e867e8-bcde-43a2-adc7-c80b0948e85f /app ext4 noatime,usrquota,grpquota 1 2
uuid=1d6cbe88-ffb4-4adf-bacf-76be1fa75708 /boot ext4 defaults 1 2
#uuid=b2c064f5-1ee5-4b5c-9e75-ed41cb99c5aa swap swap defaults 0 0
#uuid=a0516c4f-40e6-4919-905a-8b44db12ff7b swap swap defaults,pri=0 0 0
#/dev/sdb2 /test ext4 rw,seclabel,relatime,data=ordered 0 0
#/dev/sdb1 /home xfs rw,seclabel,relatime,attr2,inode64,usrquota,grpquota 0 0
[root@centos7 mnt]$ mdadm -d # 再次查看下mdadm信息，確保沒有了
mdadm: no devices given.
[root@centos7 mnt]$ mdadm --zero-superblock /dev/sd{b1,b2,c1,c2,d1,e1} # 請求md的元數據信息
以上就是我們給大家整理的在linux磁盤管理中實現軟raid的方法講解，大家有不明白的可以在下方的留言區討論。
原文鏈接：http://www.cnblogs.com/zhaojiedi1992/p/zhaojiedi_linux_041_raid.html
