LVM管理创建PV阶段报错：Device /dev/sda* not found (or ignored by filtering)

用 fdisk 创建 4 个分区，然后创建 PV，发现错误如下：

[root@DB lvm]# pvcreate /dev/sda{7,8,9,10}
  Device /dev/sda7 not found (or ignored by filtering).
  Device /dev/sda8 not found (or ignored by filtering).
  Device /dev/sda9 not found (or ignored by filtering).
  Device /dev/sda10 not found (or ignored by filtering).

 查了一下资料，说要先执行 dd if=/dev/urandom 把/dev/sda覆盖分区块，也就是擦除分区

[root@DB lvm]# dd if=/dev/urandom of=/dev/sda7 bs=512 count=64
64+0 records in
64+0 records out
32768 bytes (33 kB) copied, 0.00416541 s, 7.9 MB/s
······省······
[root@DB lvm]# dd if=/dev/urandom of=/dev/sda10 bs=512 count=64
64+0 records in
64+0 records out
32768 bytes (33 kB) copied, 0.00416541 s, 7.9 MB/s

[root@DB lvm]# pvcreate /dev/sda7
  Physical volume "/dev/sda7" successfully created.

[root@DB lvm]# pvcreate /dev/sda{8,9,10}
  Can't open /dev/sda8 exclusively.  Mounted filesystem?

     发现 /dev/sda7 可以创建 PV，但是 /dev/sda{8,9,10} 提示 Mounted filesystem? 我的磁盘是新分割出来的啊?

赶紧看看 /dev/sda{8,9,10} 有没有被挂载

[root@DB ~]# df
Filesystem                1K-blocks    Used Available Use% Mounted on
/dev/sda2                  10190136 5686280   3979568  59% /
/dev/sda1                    999320  130800    799708  15% /boot
/dev/mapper/centos00-home   5029504  283860   4467116   6% /home
/dev/sr0                    4414592 4414592         0 100% /run/media/CentOS 7 x86_64
······省······

[root@DB lvm]# lsblk
NAME              MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINT
sda                 8:0    0   25G  0 disk  
├─sda1              8:1    0    1G  0 part  /boot
├─sda2              8:2    0   10G  0 part  /
├─sda3              8:3    0    5G  0 part  
│ └─centos00-home 253:0    0    5G  0 lvm   /home
├─sda4              8:4    0  512B  0 part  
├─sda5              8:5    0    2G  0 part  [SWAP]
├─sda6              8:6    0    1M  0 part  
├─sda7              8:7    0    1G  0 part  
├─sda8              8:8    0    1G  0 part  
│ └─md0             9:0    0    3G  0 raid5 
├─sda9              8:9    0    1G  0 part  
│ └─md0             9:0    0    3G  0 raid5 
└─sda10             8:10   0    1G  0 part  
  └─md0             9:0    0    3G  0 raid5 

      用 df 指令没有发现异常，但是用 lsblk 确实发现 /dev/sda{8,9,10} 已经挂载到了 raid。

[root@DB tmp]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sda8[1] sda10[5] sda9[2]
      3142656 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [_UUU]
      
unused devices: <none>

      我之前的确用 /dev/sda{7,8,9,10} 做了raid5 实验，但是已经停掉，

      并且分区也是重新删了再创建一遍，为什么还会挂载上呢？难道是错误的操作导致的？

尝试再次关闭 raid

[root@DB tmp]# mdadm --stop /dev/md0
mdadm: stopped /dev/md0
[root@DB tmp]# mdadm --zero-superblock /dev/sda{8,9,10}
mdadm: Unrecognised md component device - /dev/sda8
mdadm: Unrecognised md component device - /dev/sda9
mdadm: Unrecognised md component device - /dev/sda10
[root@DB tmp]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sda8[1] sda10[5] sda9[2]
      3142656 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [_UUU]
      
unused devices: <none>

      但是问题还是没有解决。但发现 /dev/md0 的挂载目录 /mnt/raid 还在

[root@DB mnt]# ls -l
drwxr-xr-x. 2 root root 4096 Nov 21 17:57 raid

尝试删除 raid 目录

[root@DB mnt]# rm -rf raid
[root@DB tmp]# lsblk
NAME              MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                 8:0    0   25G  0 disk 
├─sda1              8:1    0    1G  0 part /boot
├─sda2              8:2    0   10G  0 part /
├─sda3              8:3    0    5G  0 part 
│ └─centos00-home 253:0    0    5G  0 lvm  /home
├─sda4              8:4    0  512B  0 part 
├─sda5              8:5    0    2G  0 part [SWAP]
├─sda6              8:6    0    1M  0 part 
├─sda7              8:7    0    1G  0 part 
├─sda8              8:8    0    1G  0 part 
├─sda9              8:9    0    1G  0 part 
└─sda10             8:10   0    1G  0 part 

      这下清净了。

重新创建 PV

[root@DB tmp]# pvcreate /dev/sda{8,9,10}
  Physical volume "/dev/sda8" successfully created.
  Physical volume "/dev/sda9" successfully created.
  Physical volume "/dev/sda10" successfully created.

总结：

/dev/sda{7,8,9,10} 之前做过 raid 实验，应该是我的错误操作，导致 raid 没有完整卸载，同一分区当然同时用来做 raid 和 LVM。