linux raid配置
实验环境，red hat5 ，使用4个分好的区，代表4块磁盘，做一个raid5，查看linux下raid现象。
假设现在系统有4块磁盘，做一个raid5存放数据，3块盘构建一个raid5，另一块做热备。
一、创建部分。
1、在使用磁盘时，需要先将磁盘的分区类型改成linux raid auto类型的。
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): 7
Hex code (type L to list codes): fd
Changed system type of partition 7 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sdb: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 2610 20964793+ 5 Extended
/dev/sdb5 1 13 104359+ fd Linux raid autodetect
/dev/sdb6 14 26 104391 fd Linux raid autodetect
/dev/sdb7 27 39 104391 fd Linux raid autodetect
/dev/sdb8 40 52 104391 fd Linux raid autodetect
Command (m for help):
查看一下改好后的磁盘情况。
[root@zhaoyun ~]# fdisk -l
Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3916 31455238+ 83 Linux
Disk /dev/sdb: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 2610 20964793+ 5 Extended
/dev/sdb5 1 13 104359+ fd Linux raid autodetect
/dev/sdb6 14 26 104391 fd Linux raid autodetect
/dev/sdb7 27 39 104391 fd Linux raid autodetect
/dev/sdb8 40 52 104391 fd Linux raid autodetect
2、开始创建raid。
使用mdadm创建raid
mdadm -C /dev/md0 -l 5 -n 3 -x 1 /dev/sdb{5..8}
-C 创建
-l 类型，raid几就写几
-n 磁盘数量，最少3块，
-x 热备数量 ，按实际写，
[root@zhaoyun ~]# mdadm -C /dev/md0 -l 5 -n 3 -x 1 /dev/sdb{5..8}
cat mdadm: array /dev/md0 started.
[root@zhaoyun ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdb7[2] sdb8[3](S) sdb6[1] sdb5[0]
208512 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
[root@zhaoyun ~]# mdadm -D /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Tue Nov 29 09:39:50 2011
Raid Level : raid5
Array Size : 208512 (203.66 MiB 213.52 MB)
Used Dev Size : 104256 (101.83 MiB 106.76 MB)
Raid Devices : 3
Total Devices : 4
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Tue Nov 29 09:39:53 2011
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
UUID : 0eaef563:3d63e66d:52b3a5c7:ff502931
Events : 0.2
Number Major Minor RaidDevice State
0 8 21 0 active sync /dev/sdb5
1 8 22 1 active sync /dev/sdb6
2 8 23 2 active sync /dev/sdb7
3 8 24 - spare /dev/sdb8
3、遮掩raid就创建好了，下面格式化使用。
[root@zhaoyun ~]# mkfs.ext3 /dev/md0
[root@zhaoyun ~]# mount /dev/md0 /mnt/
[root@zhaoyun ~]# cd /mnt
[root@zhaoyun mnt]# ls
lost+found
可以看到新创建的raid5容量是200M的，但实际创建的时候给了300M ，这是raid5的特性，n分之n-1.的容量。
[root@zhaoyun mnt]# df -h
文件系统 容量 已用 可用 已用% 挂载点
/dev/sda1 30G 3.1G 25G 12% /
tmpfs 95M 0 95M 0% /dev/shm
/dev/hdc 2.8G 2.8G 0 100% /media
/dev/md0 198M 5.8M 182M 4% /mnt
[root@zhaoyun mnt]# touch file
[root@zhaoyun mnt]# ls
file lost+found
[root@zhaoyun mnt]#
如果不生成配置文件重启后raid就看不见了。
4、生成mdadm配置文件
[root@zhaoyun ~]# mdadm -D --scan >> /etc/mdadm.conf
[root@zhaoyun ~]# cat /etc/mdadm.conf
ARRAY /dev/md0 level=raid5 num-devices=3 metadata=0.90 spares=2 UUID=68f3eb1f:adeffa6b:bd57a6e6:436b9c07
[root@zhaoyun ~]#
5、raid的配置完成。
二、实验raid是否好使。
1、模拟坏掉一块磁盘。查看热备的效果。
[root@zhaoyun ~]# mdadm /dev/md0 -f /dev/sdb5
mdadm: set /dev/sdb5 faulty in /dev/md0
[root@zhaoyun ~]# mdadm -D /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Tue Nov 29 09:44:47 2011
Raid Level : raid5
Array Size : 208512 (203.66 MiB 213.52 MB)
Used Dev Size : 104256 (101.83 MiB 106.76 MB)
Raid Devices : 3
Total Devices : 5
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Tue Nov 29 09:57:17 2011
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 4
Failed Devices : 1
Spare Devices : 2
Layout : left-symmetric
Chunk Size : 64K
Rebuild Status : 70% complete
UUID : 68f3eb1f:adeffa6b:bd57a6e6:436b9c07
Events : 0.8
Number Major Minor RaidDevice State
3 8 24 0 spare rebuilding /dev/sdb8 #将热备的硬盘加入到raid中，必经过的状态
1 8 22 1 active sync /dev/sdb6
2 8 23 2 active sync /dev/sdb7
4 8 25 - spare /dev/sdb9
5 8 21 - faulty spare /dev/sdb5 #顺坏硬盘的状态
[root@zhaoyun ~]# mdadm -D /dev/md0
/dev/md0:
Version : 0.90
Creation Time : Tue Nov 29 09:44:47 2011
Raid Level : raid5
Array Size : 208512 (203.66 MiB 213.52 MB)
Used Dev Size : 104256 (101.83 MiB 106.76 MB)
Raid Devices : 3
Total Devices : 5
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Tue Nov 29 09:57:20 2011
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 1
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
UUID : 68f3eb1f:adeffa6b:bd57a6e6:436b9c07
Events : 0.10
Number Major Minor RaidDevice State
0 8 24 0 active sync /dev/sdb8 #重建完成后的状态。
1 8 22 1 active sync /dev/sdb6
2 8 23 2 active sync /dev/sdb7
3 8 25 - spare /dev/sdb9
4 8 21 - faulty spare /dev/sdb5
[root@zhaoyun ~]#
mdadm -S /dev/md0 停止raid
mdadm -A /dev/md0 启动raid
mdadm --zero-superblock /dev/sdb{5..9}
mdadm -G /dev/md0 -n 4
mdadm /dev/md5 -a /dev/sdb 0
本文转自zhaoyun00 51CTO博客，原文链接:http://blog.51cto.com/zhaoyun/730397
