报错：
#pvcreate /dev/dfb2 /dev/dfa2 /dev/dfc2 /dev/dfd2 already exists in filesystem
Can't open /dev/dfa2 exclusively. Mounted filesystem?
Can't open /dev/dfb2 exclusively. Mounted filesystem?
Can't open /dev/dfc2 exclusively. Mounted filesystem?
Can't open /dev/dfd2 exclusively. Mounted filesystem?
Device already not found (or ignored by filtering).
Device exists not found (or ignored by filtering).
Device in not found (or ignored by filtering).
Device filesystem not found (or ignored by filtering).
解决方案：
LVM 'Can’t open /dev/sdb1 exclusively. Mounted filesystem?' Problem
27 Jun 2014
在将几块盘做LVM时，遇到一个之前都没遇到过的问题:
root@ubuntu:~# pvcreate /dev/sdc1
Can't open /dev/sdc1 exclusively. Mounted filesystem?
首先第一反应就是查看这个分区是否已经在使用了，但是没有。
查看硬盘的一些信息:
root@ubuntu:~# cat /proc/partitions
major minor #blocks name
80 488386584 sda
8 116777216 sda1
8 2471608344 sda2
832 488386584 sdc
833 488386584 sdc1
816 488386584 sdb
817 488385560 sdb1
848 488386584 sdd
849 488384001 sdd1
254 0838860800 dm-0
254 14194304 dm-1
254 2488386584 dm-2
254 3488386584 dm-3
254 5488384001 dm-5
254 4488384001 dm-4
root@ubuntu:~# fdisk /dev/sdc -l
Disk /dev/sdc: 500.1 GB, 500107862016 bytes
81 heads, 63 sectors/track, 191411 cylinders, total 976773168 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 identifier: 0xbbbab9b8
Device Boot Start End BlocksId System
/dev/sdc1 2048 976773167488385560 8e Linux LVM
接着看一些底层的信息:
dmsetup 是一个底层的逻辑卷管理， dm 应该是 Device Mapper的简称。
root@ubuntu:~# dmsetup status
35000c50026716847: 0 976773168 multipath 2 0 0 0 1 1 A 0 1 0 8:48 A 0
vg_data-lv_home: 0 976764928 linear
vg_data-lv_home: 976764928 700956672 linear
35000c5002670f03e: 0 976773168 multipath 2 0 0 0 1 1 A 0 1 0 8:32 A 0
35000c5002670f03e-part1: 0 976768002 linear
35000c50026716847-part1: 0 976768002 linear
vg_data-lv_swap: 0 8388608 linear
root@ubuntu:~# dmsetup ls
35000c50026716847 (254, 2)
vg_data-lv_home (254, 0)
35000c5002670f03e (254, 3)
35000c5002670f03e-part1 (254, 5)
35000c50026716847-part1 (254, 4)
vg_data-lv_swap (254, 1)
可以看到 35000c5002670f03e 和 35000c50026716847 组成了multipath(多路径)
root@ubuntu:~# multipath -ll
35000c50026716847 dm-2 ATA,GB0500EAFJH
size=466G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
`- 3:0:0:0 sdd 8:48 active ready running
35000c5002670f03e dm-3 ATA,GB0500EAFJH
size=466G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
`- 2:0:0:0 sdc 8:32 active ready running
root@ubuntu:~# ll /dev/mapper/
total 0
drwxr-xr-x 2 root root 180 Jun 28 01:39 ./
drwxr-xr-x 14 root root 13060 Jun 28 17:17 ../
lrwxrwxrwx 1 root root 7 Jun 28 01:39 35000c5002670f03e -> ../dm-3
lrwxrwxrwx 1 root root 7 Jun 28 01:39 35000c5002670f03e-part1 -> ../dm-5
lrwxrwxrwx 1 root root 7 Jun 28 01:39 35000c50026716847 -> ../dm-2
lrwxrwxrwx 1 root root 7 Jun 28 01:39 35000c50026716847-part1 -> ../dm-4
crw------T 1 root root 10, 236 Jun 28 01:39 control
lrwxrwxrwx 1 root root 7 Jun 28 01:39 vg_data-lv_home -> ../dm-0
lrwxrwxrwx 1 root root 7 Jun 28 01:39 vg_data-lv_swap -> ../dm-1
使用 dmsetup remove xxx 移除掉就可以创建PV了:
root@ubuntu:~# dmsetup remove 35000c5002670f03e-part1
root@ubuntu:~# dmsetup remove 35000c5002670f03e
root@ubuntu:~# pvcreate /dev/sdc1
Physical volume "/dev/sdc1" successfully created
也可以使用dmsetup remove_all移除所有。
TODO: 继续研究