小知识:linux磁盘管理软RAID的实现原理分析和方法分享

1 什么是raid

raid全称是独立磁盘冗余阵列(redundant array of independent disks),基本思想是把多个磁盘组合起来,组合一个磁盘阵列组,使得性能大幅提高。

raid分为几个不同的等级,各个不同的等级均在数据可靠性及读写性能做了不同的权衡。实际工作中根据自己的业务需求选择不同的raid方案。

2 raid的实现方式

外接式磁盘阵列:通过扩展卡提供适配能力内接式raid:主板集成raid控制器安装os前在bios里配置软件raid:通过os实现

3 标准的raid

3.1 raid0

raid0称为条带化存储,将数据分段存储在各个磁盘中,读写均可以并行处理,因此读写速率为单个磁盘的n倍,没有冗余功能,任何一个磁盘的损坏就会导致的数据不可用。

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3.2 raid1

radi1是镜像存储,没有数据校验,数据被同等的写入到2个或者多个磁盘中,写入速度相对慢, 但是读取速度比较快。

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3.3 raid 4

radi4在raid1的基础上,n个盘用于数据存储,另外加入了1个磁盘作为校验盘。一共n+1个盘,任何一个盘坏掉也不影响数据的访问

3.4 raid 5

raid5在raid4的基础上,由原来的一个盘来存储校验数据,改为每个盘都有数据和校验信息的。

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4 混合raid

4.1 raid01

先组成raid0,然后组成raid1.

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4.2 raid10

先组成raid1,然后组成raid0

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5 软raid的实现

5.1 raid5的实现

创建由三块硬盘组成的可用空间为2g的raid5设备,要求其chunk大小为256k,文件系统为ext4,开机可自动挂载至/mydata目录

5.1.1 先看看我们的磁盘情况

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[root@centos7 bash]$ lsblk
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
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 

这里我们使用sdb,sdc,sdd,每个盘创建一个主分区1g,构建radi5.

5.1.2 根据实际情况分区

[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 创建raid

[root@centos7 bash]$ mdadm -c /dev/md5 -a yes -l 5 -n 3 /dev/sd{b1,c1,d1} -c 256 # -c指定创建, -a yes 自动创建设备 , -l 设定level , -n 设定磁盘个数, -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 # 将软raid信息写入到配置文件中去 [root@centos7 bash]$ mkdir /mnt/md5 # 创建挂载点目录 [root@centos7 bash]$ mkfs.ext4 /dev/md5 # 创建文件系统 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 # 挂载设备 [root@centos7 bash]$ tail -n 1 /etc/mtab /dev/md5 /mnt/md5 ext4 rw,seclabel,relatime,stripe=128,data=ordered 0 0 # 查看挂载信息 [root@centos7 bash]$ tail -n 1 /etc/mtab >>/etc/fstab #添加到fstab文件中,确保开机启动,这里建议使用uuid

5.1.4 验证raid

[root@centos7 md5]$ mdadm -d /dev/md5 #查看详细raid5详细信息,可以发现有3个都是working状态的 /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 设定指定设备故障, 将/dev/sdc1 这个盘标记失败, 看是否数据能访问,我这里使用-f标记失败,工作中可以根据硬盘指示灯判断磁盘状态 mdadm: set /dev/sdc1 faulty in /dev/md5 [root@centos7 md5]$ mdadm -d /dev/md5 #在次查看信息,发现工作的是2个, 一个失败的设备 /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 # 这里注意了。 我们的一个盘坏掉了。 raid5状态为降级使用了。 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 # 发现我们的数据还是能访问的。没有问题。

5.1.5 替换设备

我这里是磁盘坏掉后的执行替换的, 完全可以多一个备用盘, 坏掉自动替换的。

[root@centos7 md5]$ mdadm /dev/md5 -a /dev/sde1 # 上面我们的sdc1数据损坏,我们需要更换新的磁盘来顶替他的位置。这里添加一个sde1的磁盘, fdisk操作这里省去了。 mdadm: added /dev/sde1 [root@centos7 md5]$ mdadm -ds # 查看详细信息 array /dev/md5 metadata=1.2 name=centos7.magedu.com:5 uuid=2c8ae60d:a799fcb7:9008a046:ae6ea430 [root@centos7 md5]$ mdadm -d /dev/md5 # 查看详细信息 /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 # 状态恢复正常了。没有问题 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 # 这个盘是坏掉的,我们已经加入了新的磁盘, 这个盘可以干掉了 [root@centos7 md5]$ man mdadm [root@centos7 md5]$ mdadm /dev/md5 –remove /dev/sdc1 # 这个盘我们从raid5中移除去。 mdadm: hot removed /dev/sdc1 from /dev/md5

5.1.6扩展raid

我们上面使用的是2+1构成的raid5,磁盘利用率为66%,如果我们想改成3+1 可以执行类似如下命令

[root@centos7 mnt]$ mkadm -g -r /dev/md5 -n 4 -a /dev/sdxx # 这里我就不测试了。使用/dev/sdxx代替一个设备。-g 是grown增长的意思,-r 是resizefs的意思,

5.1.7 清空raid信息

[root@centos7 mnt]$ umount /dev/md5 # 卸载设备 [root@centos7 mnt]$ mdadm -s /dev/md5 # 停止raid5 mdadm: stopped /dev/md5 [root@centos7 mnt]$ sed -i $d /etc/fstab # 删除fstab中关于raid5挂载的行 [root@centos7 mnt]$ cat /etc/fstab # 确保fstab没有大问题 # # /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 # 删除raid默认配置文件 [root@centos7 mnt]$ mdadm –zero-superblock /dev/sd{b1,e1,d1,c1} # 清空设置上的超级块信息

5.2 raid10的实现

raid10 ,6个分区,2个一组raid1,3组raid0

5.2.1 案例分析

分析下,我们创建一个raid10设置,2个设备组成一个raid1,6个设备2个一组可以组成3个raid1, 然后把3个raid1组成一个raid0即可

5.2.2 先创建6个设备

[root@centos7 mnt]$ lsblk # 就是使用fdisk 创建的设备, 具体这里就不写了。 最终使用lsblk显示,我们可以看到sdb1,sdb2,sdd1,sde1一共6个磁盘 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 创建raid

[root@centos7 mnt]$ mdadm -c /dev/md11 -a yes -l 1 -n 2 /dev/sd{b1,c1} # 创建第一个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} #创建第二个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} # 创建第三个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} # 将3个raid1 合并为一个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 # 创建文件系统 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 # 写配置文件到mdadm的配置文件中 [root@centos7 mnt]$ mkdir /mnt/md10 # 创建挂载目录 [root@centos7 mnt]$ mount /dev/md10 /mnt/md10 # 挂载文件系统 [root@centos7 mnt]$ tail -n 1 /etc/mtab # 查看mtab文件中的最后一行, 也就是我们的md10挂载信息 /dev/md10 /mnt/md10 ext4 rw,seclabel,relatime,stripe=384,data=ordered 0 0 [root@centos7 mnt]$ tail -n 1 /etc/mtab >> /etc/fstab #添加到开机启动

5.2.4 raid 清除工作

[root@centos7 mnt]$ umount /dev/md10 # 取消挂载 [root@centos7 mnt]$ rm -rf /etc/mdadm.conf # 删除mdadm的默认配置 [root@centos7 mnt]$ mdadm -s /dev/md10 # 停止raid0设置 mdadm: stopped /dev/md10 [root@centos7 mnt]$ mdadm -s /dev/md11 # 停止raid1设置 mdadm: stopped /dev/md11 [root@centos7 mnt]$ mdadm -s /dev/md12 # 停止radi1 设置 mdadm: stopped /dev/md12 [root@centos7 mnt]$ mdadm -s /dev/md13 # 停止raid 1 设置 mdadm: stopped /dev/md13 [root@centos7 mnt]$ sed -i $d /etc/fstab # 删除fstab的挂载 [root@centos7 mnt]$ cat /etc/fstab # 确保正确 # # /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,确保没有了 mdadm: no devices given. [root@centos7 mnt]$ mdadm –zero-superblock /dev/sd{b1,b2,c1,c2,d1,e1} # 请求md的元数据信息

以上就是我们给大家整理的在linux磁盘管理中实现软raid的方法讲解,大家有不明白的可以在下方的留言区讨论。

原文链接:http://www.cnblogs.com/zhaojiedi1992/p/zhaojiedi_linux_041_raid.html

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