linux磁盤管理系列二：軟RAID的實現
linux磁盤管理系列二：軟RAID的實現
1 什麼是RAID
RAID全稱是獨立磁盤冗餘陣列（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，使得性能大幅提升。html
RAID分爲幾個不一樣的等級，各個不一樣的等級均在數據可靠性及讀寫性能作了不一樣的權衡。實際工做中根據本身的業務需求選擇不一樣的RAID方案。 node
2 RAID的實現方式
- 外接式磁盤陣列：經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裏配置
- 軟件RAID：經過OS實現
3 標準的RAID
3.1 RAID0
RAID0稱爲條帶化存儲，將數據分段存儲在各個磁盤中，讀寫都可以並行處理，所以讀寫速率爲單個磁盤的N倍，沒有冗餘功能，任何一個磁盤的損壞就會致使的數據不可用。linux
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， 可是讀取速度比較快。centos
3.3 RAID 4
RADI4在RAID1的基礎上，N個盤用於數據存儲，另外加入了1個磁盤做爲校驗盤。一共N+1個盤，任何一個盤壞掉也不影響數據的訪問app
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，改成每一個盤都有數據和校驗信息的。ide
4 混合RAID
4.1 RAID01
先組成RAID0,而後組成RAID1.性能
4.2 RAID10
先組成RAID1,而後組成RAID0測試
5 軟RAID的實現
5.1 RAID5的實現
建立由三塊硬盤組成的可用空間爲2G的RAID5設備，要求其chunk大小爲256k，文件系統爲ext4，開機可自動掛載至/mydata目錄ui
5.1.1 先看看咱們的磁盤狀況
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這裏咱們使用sdb,sdc,sdd,每一個盤建立一個主分區1G,構建RADI5.
5.1.2 根據實際狀況分區
[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 建立raid
[root@centos7 Bash]$ mdadm -C /dev/md5 -a yes -l 5 -n 3 /dev/sd{b1,c1,d1} -c 256 # -C指定建立， -a yes 自動建立設備 ， -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 # 建立掛載點目錄
[root@centos7 Bash]$ mkfs.ext4 /dev/md5 # 建立文件系統
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，確保開機啓動，這裏建議使用uuid
5.1.4 驗證raid
[root@centos7 md5]$ mdadm -D /dev/md5 #查看詳細raid5詳細信息，能夠發現有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，我這裏使用-f標記失敗，工做中能夠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，發現工做的是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 # 這裏注意了。 咱們的一個盤壞掉了。 raid5狀態爲降級使用了。
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 # 發現咱們的數據仍是能訪問的。沒有問題。
5.1.5 替換設備
我這裏是磁盤壞掉後的執行替換的， 徹底能夠多一個備用盤， 壞掉自動替換的。
[root@centos7 md5]$ mdadm /dev/md5 -a /dev/sde1 # 上面咱們的sdc1數據損壞，咱們須要更換新的磁盤來頂替他的位置。這裏添加一個sde1的磁盤， fdisk操做這裏省去了。
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，咱們已經加入了新的磁盤， 這個盤能夠幹掉了
[root@centos7 md5]$ man mdadm
[root@centos7 md5]$ mdadm /dev/md5 --remove /dev/sdc1 # 這個盤咱們從raid5中移除去。
mdadm: hot removed /dev/sdc1 from /dev/md5
5.1.6擴展raid
咱們上面使用的是2+1構成的raid5,磁盤利用率爲66%，若是咱們想改爲3+1 能夠執行相似以下命令
[root@centos7 mnt]$ mkadm -G -r /dev/md5 -n 4 -a /dev/sdxx # 這裏我就不測試了。使用/dev/sdxx代替一個設備。-G 是Grown增加的意思，-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 # 中止raid5 mdadm: stopped /dev/md5 [root@centos7 mnt]$ sed -i '$d' /etc/fstab # 刪除fstab中關於raid5掛載的行 [root@centos7 mnt]$ 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，咱們建立一個raid10設置，2個設備組成一個raid1,6個設備2個一組能夠組成3個raid1, 而後把3個raid1組成一個raid0便可
5.2.2 先建立6個設備
[root@centos7 mnt]$ lsblk # 就是使用fdisk 建立的設備， 具體這裏就不寫了。 最終使用lsblk顯示，咱們能夠看到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 建立raid
[root@centos7 mnt]$ mdadm -C /dev/md11 -a yes -l 1 -n 2 /dev/sd{b1,c1} # 建立第一個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} #建立第二個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} # 建立第三個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 合併爲一個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 # 建立文件系統
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 # 建立掛載目錄
[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文件中的最後一行， 也就是咱們的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 #添加到開機啓動
5.2.4 raid 清除工做
[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 # 中止raid0設置
mdadm: stopped /dev/md10
[root@centos7 mnt]$ mdadm -S /dev/md11 # 中止raid1設置
mdadm: stopped /dev/md11
[root@centos7 mnt]$ mdadm -S /dev/md12 # 中止radi1 設置
mdadm: stopped /dev/md12
[root@centos7 mnt]$ mdadm -S /dev/md13 # 中止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
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