解决"/dev/sdX is apparently in use by the systemwill not make a filesystem here"
在Linux上配置multipath，在HP EVA存储上划分一个100G大小的LUN,然后把它映射给Linux主机，将该100G空间使用fdisk进行分区，分为3个区（关于Linux multipath多路径配置与使用案例请参考作者的另一篇博文：http://blog.itpub.net/31015730/viewspace-2146732/）
[root@seaing mapper]# cat /proc/partitions
major minor #blocks name
8 0 488386584 sda
8 1 104391 sda1
8 2 488279610 sda2
8 16 104857600 sdb
8 17 48837568 sdb1
8 18 29302560 sdb2
8 19 19543072 sdb3
8 32 209715200 sdc
8 48 104857600 sdd
8 49 48837568 sdd1
8 50 29302560 sdd2
8 51 19543072 sdd3
8 64 209715200 sde
8 80 104857600 sdf
8 81 48837568 sdf1
8 82 29302560 sdf2
8 83 19543072 sdf3
8 96 209715200 sdg
8 112 104857600 sdh
8 113 48837568 sdh2
8 114 29302560 sdh3
8 115 19543072 sdh4
8 128 209715200 sdi
253 0 469794816 dm-0
253 1 18481152 dm-1
253 2 104857600 dm-2
253 3 209715200 dm-3
但是在格式化文件系统的时候，出现了报错
[root@seaing mapper]# mkfs.ext3 /dev/sdb1
mke2fs 1.39 (29-May-2006)
/dev/sdb1 is apparently in use by the system; will not make a filesystem here!
提示/dev/sdb1 正在被使用。 /dev/sdb1 正在被DM管理，所以我们创建文件系统时提示报错，我们手工的移除，就可以正常的创建文件系统，具体操作如下：
[root@seaing mapper]# dmsetup status
mpath3: 0 419430400 multipath 2 0 0 0 2 1 A 0 2 0 8:64 A 0 8:128 A 0 E 0 2 0 8:32 A 0 8:96 A 0
mpath2: 0 209715200 multipath 2 0 0 0 2 1 A 0 2 0 8:16 A 0 8:80 A 0 E 0 2 0 8:48 A 0 8:112 A 0
VolGroup00-LogVol01: 0 36962304 linear
VolGroup00-LogVol00: 0 939589632 linear
[root@seaing mapper]# mkdir /dev/mapper/mpath2 /comsys/
mkdir: cannot create directory `/dev/mapper/mpath2': File exists
mkdir: cannot create directory `/comsys/': File exists
[root@seaing mapper]#
[root@seaing mapper]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
434G 4.9G 407G 2% /
/dev/sda1 99M 18M 77M 19% /boot
tmpfs 7.9G 0 7.9G 0% /dev/shm
[root@seaing mapper]#
[root@seaing mapper]#
[root@seaing mapper]# mount /dev/mapper/mpath2 /comsys/
mount: you must specify the filesystem type
[root@seaing mapper]# mount /dev/sdb1 /comsys/
mount: /dev/sdb1 already mounted or /comsys/ busy
删除映射关系，取消映射
[root@seaing mapper]# dmsetup remove_all（或dmsetup remove mpath2）
[root@seaing mapper]#
[root@seaing mapper]# dmsetup status
VolGroup00-LogVol01: 0 36962304 linear
VolGroup00-LogVol00: 0 939589632 linear
[root@seaing mapper]#
[root@seaing mapper]# ll /dev/mapper
total 0
crw------- 1 root root 10, 63 Oct 24 18:02 control
brw-rw---- 1 root disk 253, 0 Oct 24 18:02 VolGroup00-LogVol00
brw-rw---- 1 root disk 253, 1 Oct 24 18:02 VolGroup00-LogVol01
再次创建文件系统，创建成功
[root@seaing mapper]# mkfs.ext3 /dev/sdb1
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
6111232 inodes, 12209392 blocks
610469 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
373 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 33 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
挂载成功
[root@seaing mapper]# mount /dev/sdb1 /comsys/
[root@seaing mapper]#
[root@seaing mapper]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
434G 4.9G 407G 2% /
/dev/sda1 99M 18M 77M 19% /boot
tmpfs 7.9G 0 7.9G 0% /dev/shm
/dev/sdb1 46G 181M 44G 1% /comsys
设置为开机挂载
[root@seaing mapper]# vi /etc/fstab
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/VolGroup00/LogVol01 swap swap defaults 0 0
/dev/sdb1 /comsys ext3 defaults 0 0
重新启动操作系统，查看自动挂载是否成功
[root@seaing /]# reboot
Broadcast message from root (pts/1) (Wed Oct 25 10:16:35 2017):
The system is going down for reboot NOW!
Last login: Wed Oct 25 08:54:28 2017 from 10.1.1.44
[root@seaing ~]# cd /dev/mapper/
[root@seaing mapper]#
[root@seaing mapper]# ll
total 0
crw------- 1 root root 10, 63 Oct 25 10:19 control
brw-rw---- 1 root disk 253, 2 Oct 25 10:19 mpath2
brw-rw---- 1 root disk 253, 4 Oct 25 10:19 mpath2p1
brw-rw---- 1 root disk 253, 5 Oct 25 10:19 mpath2p2
brw-rw---- 1 root disk 253, 6 Oct 25 10:19 mpath2p3
brw-rw---- 1 root disk 253, 3 Oct 25 10:19 mpath3
brw-rw---- 1 root disk 253, 0 Oct 25 10:19 VolGroup00-LogVol00
brw-rw---- 1 root disk 253, 1 Oct 25 10:19 VolGroup00-LogVol01
[root@seaing mapper]#
[root@seaing mapper]# ll /dev/mpath/
total 0
lrwxrwxrwx 1 root root 7 Oct 25 10:19 mpath2 -> ../dm-2
lrwxrwxrwx 1 root root 7 Oct 25 10:19 mpath2p1 -> ../dm-4
lrwxrwxrwx 1 root root 7 Oct 25 10:19 mpath2p2 -> ../dm-5
lrwxrwxrwx 1 root root 7 Oct 25 10:19 mpath2p3 -> ../dm-6
lrwxrwxrwx 1 root root 7 Oct 25 10:19 mpath3 -> ../dm-3
重启后测试，该文件不能正常挂载，手工挂载也会失败。
[root@seaing mapper]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
434G 4.9G 407G 2% /
/dev/sda1 99M 18M 77M 19% /boot
tmpfs 7.9G 0 7.9G 0% /dev/shm
手动挂载也不能成功
[root@seaing mapper]# mount -a
mount: /dev/sdb1 already mounted or /comsys busy
所以说这种方法只能暂时性挂载，个人觉得不太不可取！！！想要永久的进行挂载，还是按照作者的另一篇博文（http://blog.itpub.net/31015730/viewspace-2146732/）的方法进行比较稳妥一点。
作者：SEian.G（苦练七十二变，笑对八十一难）