一、RAID简介
RAID是“Redundant Array of Independent Disk”的缩写，中文意思是独立冗余磁盘阵列，早期称为廉价磁盘阵列。简单地解释，就是将N台硬盘通过RAID Controller（分Hardware，Software）结合成虚拟单台大容量的硬盘使用。RAID技术大致分为两种：基于硬件的RAID技术和基于软件的RAID技术。
二、RAID术语
RAID0
raid0: 读、写性能提升，无容错能力，空间n*disk
RAID1
raid1: 写性能略有下降，读性能提升，容错，空间：1*disk
RAID4
raid4: 读、写性能提升，有容错能力（最多坏一块磁盘），空间：(n-1)*disk
RAID5
raid5: 读、写性能提升，有容错能力（最多坏一块磁盘），空间：(n-1)*disk
RAID10
raid10: 读、写性能提升，有容错能力（每一组可坏一块盘），空间：n*disk/2
三、RAID的基本命令
mdadm工具： md: 支持将任何块设备组织成RAID mdadm: 模块式化命令 -A: 装配模式，重新识别此前实现的RAID -C：创建模式，创建RAID -F：监控模式 管理模式：-f, -r, -a -C: 创建模式中专用选项 -n #: 用于创建RAID设备的磁盘个数； -l #: 级别 -a yes: 自动为创建的RAID生成设备文件; -c Chunk_Size: md设备的设备文件，一般在/dev目录下，以md开头，后跟一个数字来区别
[[email protected] tmp]# rpm -qa mdadm 查询是否安装了支持raid的软件
mdadm-3.2.6-7.el6.x86_64
五、实验
实验是划分四个5g的硬盘，演示raid的创建、热备盘、停止、添加、重新装配
1、添加磁盘用虚拟机添加一个20g的硬盘，此处省略
2、创建分区
[[email protected] ~]# fdisk /dev/sdb Command (m for help): n 创建主分区 Command action e extended 逻辑分区 p primary partition (1-4) p Partition number (1-4): 1 第一个分区 First cylinder (1-2610, default 1): 开始块 Using default value 1 Last cylinder, +cylinders or +size{K,M,G} (1-2610, default 2610): +5G 划分5G容量 Command (m for help): t 修改文件类型 Selected partition 1 Hex code (type L to list codes): 文件类型(Linux raid autodetect) Changed system type of partition 1 to 8e ( Linux raid autodetect) Command (m for help): p 查看分区 Disk /dev/sdb: 21.5 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 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: 0xba762e8d Device Boot Start End Blocks Id System /dev/sdb1 1 654 5253223+ fd Linux raid autodetect /dev/sdb2 655 1308 5253255 fd Linux raid autodetect /dev/sdb3 1309 1962 5253255 fd Linux raid autodetect Command (m for help): w 保存分区 The partition table has been altered! 创建分区此处不再演示，照着上面的重做分好实验要求的分区 3、查看所创建分区系统是否识别到、没有识别到要 partx -a /dev/sdbx直到识别到或者重启系统。 [[email protected] ~]# cat /proc/partitions 查看创建分区 8 0 83886080 sda 8 1 204800 sda1 8 2 62914560 sda2 8 3 39163 sda3 8 4 1 sda4 8 5 40131 sda5 8 16 20971520 sdb 8 17 5253223 sdb1 8 18 5253255 sdb2 8 19 5253255 sdb3 4、创建 RAID MD5 [[email protected] ~]# mdadm -C /dev/md5 -a yes -n 3 -l 5 /dev/sdb1 /dev/sdb2 /dev/sdb3 mdadm: Defaulting to version 1.2 metadata 创建一个名叫MD5的raid自动创建、三块磁盘、级别 mdadm: array /dev/md5 started. 为五 添加的磁盘是/dev/sdb1 /dev/sdb2 /dev/sdb3 mdadm: array /dev/md5 started. [[email protected] ~]# cat /proc/mdstat 查看创建信息 Personalities : [raid6] [raid5] [raid4] md5 : active raid5 sdb3[3] sdb2[1] sdb1[0] 10498048 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_] [=>...................] recovery = 5.9% (311296/5249024) finish=3.6min speed=22235K/sec unused devices: <none> 5、格式化挂载 [[email protected] ~]# mke2fs -t ext4 /dev/md5 格式化 mke2fs 1.41.12 (17-May-2010) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=128 blocks, Stripe width=256 blocks 657072 inodes, 2624512 blocks 131225 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2688548864 81 block groups 32768 blocks per group, 32768 fragments per group 8112 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 23 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. [[email protected] ~]# mkdir /tmp/user1 创建目录 [[email protected] ~]# mount /dev/md5 //tmp/user1 挂载 [[email protected] ~]# mount 查看挂载信息 /dev/mapper/vg0-root on / type ext4 (rw) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) tmpfs on /dev/shm type tmpfs (rw) /dev/sda1 on /boot type ext4 (rw) /dev/mapper/vg0-usr on /usr type ext4 (rw) /dev/mapper/vg0-var on /var type ext4 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) /dev/md5 on /tmp/user1 type ext4 (rw) [[email protected] ~]# df -lh 查看 RAID md5 信息 Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg0-root 20G 406M 19G 3% / tmpfs 935M 0 935M 0% /dev/shm /dev/sda1 194M 35M 150M 19% /boot /dev/mapper/vg0-usr 9.9G 2.0G 7.4G 21% /usr /dev/mapper/vg0-var 20G 305M 19G 2% /var /dev/md5 9.9G 151M 9.3G 2% /tmp/user1 [[email protected] ~]# df -lh /dev/md5 Filesystem Size Used Avail Use% Mounted on /dev/md5 9.9G 151M 9.3G 2% /tmp/user1 [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 级别 Array Size : 10498048 (10.01 GiB 10.75 GB) 容量 Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 几块 Total Devices : 3 Persistence : Superblock is persistent Update Time : Sat Jul 12 06:59:10 2014 State : clean Active Devices : 3 活动三块 Working Devices : 3 工作三块 Failed Devices : 0 停止工作0块 Spare Devices : 0 热备0块 Layout : left-symmetric Chunk Size : 512K Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 24 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 那几块磁盘在工作 6、新增一块做热备及演示磁盘坏盘，添加，移除 重新添加一块磁盘分区此处不做演示、上面照做 [[email protected] ~]# kpartx -af /dev/sda6 添加sda6这块硬盘 [[email protected] ~]# mdadm /dev/md5 -f /dev/sdb1 模拟sdb1 坏掉 mdadm: set /dev/sdb1 faulty in /dev/md5 [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 3 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:23:03 2014 State : clean, degraded Active Devices : 2 Working Devices : 2 Failed Devices : 1 坏一块磁盘的表现 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 26 Number Major Minor RaidDevice State 0 0 0 0 removed 提示 removed 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 0 8 17 - faulty /dev/sdb1 提示sdb1坏掉 [[email protected] ~]# mdadm /dev/md5 -r /dev/sdb1 移除坏掉的sdb1 mdadm: hot removed /dev/sdb1 from /dev/md5 [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 2 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:23:24 2014 State : clean, degraded Active Devices : 2 Working Devices : 2 状态信息 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 29 Number Major Minor RaidDevice State 0 0 0 0 removed 坏盘已被移除 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 [[email protected] ~]# mdadm /dev/md5 -a /dev/sda6 添加一块已经分好区的硬盘带RAID MD5中 mdadm: added /dev/sda6 [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 3 总的信息 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:29:33 2014 State : clean, degraded, recovering Active Devices : 2 Working Devices : 3 现在的信息 Failed Devices : 0 Spare Devices : 1 热备信息 Layout : left-symmetric Chunk Size : 512K Rebuild Status : 21% complete 重建信息 Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 38 Number Major Minor RaidDevice State 4 8 6 0 spare rebuilding /dev/sda6 热备重建 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 [[email protected] ~]# mdadm /dev/md5 -a /dev/sdb1 添加sdb1作为热备盘 mdadm: added /dev/sdb1 [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 4 总的信息 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:29:57 2014 State : clean, degraded, recovering Active Devices : 2 Working Devices : 4 现在的信息 Failed Devices : 0 Spare Devices : 2 热备信息 Layout : left-symmetric Chunk Size : 512K Rebuild Status : 39% complete 重建信息 Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 44 Number Major Minor RaidDevice State 4 8 6 0 spare rebuilding /dev/sda6 热备重建 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 5 8 17 - spare /dev/sdb1 空闲热备盘 7、多一块热备、盘坏了自动添加重建 [[email protected] ~]# mdadm /dev/md5 -f /dev/sda6 模拟磁盘sdb6坏掉 mdadm: set /dev/sda6 faulty in /dev/md5 [[email protected] ~]# mdadm /dev/md5 -r /dev/sda6 移除sdb6 mdadm: hot remove failed for /dev/sda6: Device or resource busy [[email protected] ~]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 4 总盘的信息 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:42:30 2014 State : clean, degraded, recovering Active Devices : 2 Working Devices : 3 Failed Devices : 1 Spare Devices : 1 工作信息 Layout : left-symmetric Chunk Size : 512K Rebuild Status : 5% complete Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 59 Number Major Minor RaidDevice State 5 8 17 0 spare rebuilding /dev/sdb1 sdb1热备自动顶上重建 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 4 8 6 - faulty /dev/sda6 提示sdb6磁盘坏掉 8、模拟停电、机器坏掉之后、停盘、重新装载 [[email protected] ~]# umount /tmp/user1 卸载 [[email protected] ~]# mount 挂载信息 /dev/mapper/vg0-root on / type ext4 (rw) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) tmpfs on /dev/shm type tmpfs (rw) /dev/sda1 on /boot type ext4 (rw) /dev/mapper/vg0-usr on /usr type ext4 (rw) /dev/mapper/vg0-var on /var type ext4 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) [[email protected] ~]# mdadm -S /dev/md5 停止 RAID MD5 mdadm: stopped /dev/md5 [[email protected] tmp]# mdadm -A /dev/md5 /dev/sdb{1,2,3} /dev/sda6 重新装载MD5 mdadm: /dev/md5 has been started with 3 drives and 1 spare. [[email protected] tmp]# mdadm --detail /dev/md5 查看 RAID md5 的详细信息 /dev/md5: Version : 1.2 Creation Time : Sat Jul 12 06:53:18 2014 Raid Level : raid5 Array Size : 10498048 (10.01 GiB 10.75 GB) Used Dev Size : 5249024 (5.01 GiB 5.38 GB) Raid Devices : 3 Total Devices : 4 总盘的信息 Persistence : Superblock is persistent Update Time : Sat Jul 12 07:52:33 2014 State : clean Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 状态信息 Layout : left-symmetric Chunk Size : 512K Name : dingchao.localdomain:5 (local to host dingchao.localdomain) UUID : 5e20abb1:5dddca66:b82c6498:32052563 Events : 84 Number Major Minor RaidDevice State 5 8 17 0 active sync /dev/sdb1 1 8 18 1 active sync /dev/sdb2 3 8 19 2 active sync /dev/sdb3 4 8 6 - spare /dev/sda6 磁盘工作状态 [[email protected] tmp]# mount /dev/md5 /tmp/user1 重新挂载就可以使用啦 [[email protected] tmp]# mount 查看挂载信息 /dev/mapper/vg0-root on / type ext4 (rw) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) tmpfs on /dev/shm type tmpfs (rw) /dev/sda1 on /boot type ext4 (rw) /dev/mapper/vg0-usr on /usr type ext4 (rw) /dev/mapper/vg0-var on /var type ext4 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) /dev/md5 on /tmp/user1 type ext4 (rw) 查看挂载信息
RAID: 组织多块硬盘当一个设备来使用
硬件RAID：
硬件控制器：创建RAID通过BIOS进行
在OS中看到的仅是一个单独的设备
软件RAID：
无需任何硬件的RAID设备，仅需多个块设备（磁盘分区即可）
在OS中看到的是多个基本的磁盘设备、磁盘分区等，而后将这多个块设备可以组织一个单独的设备使用
即为软RAID
装配模式：在某OS上创建的软件RAID，被迁移到其它主机上，并启动OS之后，Linux auto detect