用mdadm做raid实验时遇到一个问题，一直没有搞定，在网上一直也没有查到，准备问那个培训老师，结果等了半天硬是没有等到，然后又在google上搜索，终于在一个老外的BBS里发现问题原因了

问题如下：不用多加解释，相信大家都能看懂

[root@localhost ~]# mdadm -C /dev/md5  -l 5 -n 3 -x 1 /dev/sdb[5-8]

mdadm: Cannot open /dev/sdb5: Device or resource busy

mdadm: Cannot open /dev/sdb6: Device or resource busy

mdadm: Cannot open /dev/sdb7: Device or resource busy

mdadm: Cannot open /dev/sdb8: Device or resource busy

这是我第一台虚拟机，后面换了一台干净的计算机，然后实验的，单独加了三块硬盘，和前面问题基本类似，不过就是三块硬盘和三个分区的问题。

寻找问题的过程中，在网上有的人说是由于主板不支持，我感觉不大可能，还有说内核不支持的，其实最终的问题根本不是这些，而是由于/dev/md*设备被占用，只要用mdadm --stop 命令把该设备停止即可，问题就可以解决。下面是过程。

[root@localhost ~]# mdadm --stop /dev/md5

mdadm: stopped /dev/md5

[root@localhost ~]# mdadm -C /dev/md5 -l 5 -n 3 /dev/sd[bcd]

mdadm: /dev/sdb appears to be part of a raid array:

level=raid5 devices=3 ctime=Wed Dec  9 03:37:11 2009

mdadm: /dev/sdc appears to be part of a raid array:

level=raid5 devices=3 ctime=Wed Dec  9 03:37:11 2009

mdadm: /dev/sdd appears to be part of a raid array:

level=raid5 devices=3 ctime=Wed Dec  9 03:37:11 2009

Continue creating array?

Continue creating array? (y/n) y

mdadm: array /dev/md5 started.

[root@localhost ~]# mdadm --detail /dev/md5

/dev/md5:

Version : 00.90.03

Creation Time : Wed Dec  9 03:46:26 2009

Raid Level : raid5

Array Size : 2097024 (2048.22 MiB 2147.35 MB)

Used Dev Size : 1048512 (1024.11 MiB 1073.68 MB)

Raid Devices : 3

Total Devices : 3

Preferred Minor : 5

Persistence : Superblock is persistent

Update Time : Wed Dec  9 03:46:26 2009

State : clean, degraded, recovering

Active Devices : 2

Working Devices : 3

Failed Devices : 0

Spare Devices : 1

Layout : left-symmetric

Chunk Size : 64K

Rebuild Status : 55% complete

UUID : 297ef6fe:26379be0:84c578f1:21ebe5cf

Events : 0.1

Number   Major   Minor   RaidDevice State

0       8       16        0      active sync   /dev/sdb

1       8       32        1      active sync   /dev/sdc

3       8       48        2      spare rebuilding   /dev/sdd

[root@localhost ~]#

[root@localhost ~]# mdadm --detail /dev/md5

/dev/md5:

Version : 00.90.03

Creation Time : Wed Dec  9 03:46:26 2009

Raid Level : raid5

Array Size : 2097024 (2048.22 MiB 2147.35 MB)

Used Dev Size : 1048512 (1024.11 MiB 1073.68 MB)

Raid Devices : 3

Total Devices : 3

Preferred Minor : 5

Persistence : Superblock is persistent

Update Time : Wed Dec  9 03:47:34 2009

State : clean

Active Devices : 3

Working Devices : 3

Failed Devices : 0

Spare Devices : 0

Layout : left-symmetric

Chunk Size : 64K

UUID : 297ef6fe:26379be0:84c578f1:21ebe5cf

Events : 0.2

Number   Major   Minor   RaidDevice State

0       8       16        0      active sync   /dev/sdb

1       8       32        1      active sync   /dev/sdc

2       8       48        2      active sync   /dev/sdd

[root@localhost ~]# mkfs.ext3 /dev/md5

mke2fs 1.39 (29-May-2006)

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

262144 inodes, 524256 blocks

26212 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

16384 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912

Writing inode tables: done

Creating journal (8192 blocks): done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or

180 days, whichever comes first.  Use tune2fs -c or -i to override.

[root@localhost ~]# mount /dev/md5 /mnt

[root@localhost ~]# df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda2             3.8G  1.9G  1.8G  53% /

/dev/sda3             4.3G  137M  3.9G   4% /home

/dev/sda1              46M   11M   33M  24% /boot

tmpfs                 339M     0  339M   0% /dev/shm

/dev/md5              2.0G   36M  1.9G   2% /mnt

[root@localhost ~]#