现象描述：
linux一个逻辑卷lv_home丢失，无法正常挂载，之前挂载在/home目录下:
[root@VM001 ~]# cat /etc/fstab
.......
/dev/VolGroup/lv_home /home ext4 defaults 0 0查看文件系统挂载情况，发现lv_home并没有挂载：
[root@VM001 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
20G 7.3G 12G 40% /
tmpfs 3.9G 224K 3.9G 1% /dev/shm
/dev/xvda1 477M 124M 328M 28% /boot尝试手动挂载发现找不到lv_home这个逻辑卷：
[root@VM0001 ~]# mount /dev/VolGroup/lv_
lv_root lv_swap
[root@VM001 ~]# cd /dev/VolGroup/
[root@VM000000875 VolGroup]# ls
lv_root lv_swap
[root@VM001 VolGroup]# ll
total 0
lrwxrwxrwx. 1 root root 7 Jul 31 11:06 lv_root -> ../dm-0
lrwxrwxrwx. 1 root root 7 Jul 31 11:06 lv_swap -> ../dm-1查看逻辑卷状态，发现处于异常状态(NOT available)：
[root@VM001 VolGroup]# lvdisplay
.......
--- Logical volume ---
LV Path /dev/VolGroup/lv_home
LV Name lv_home
VG Name VolGroup
LV UUID 4rdajn-62q9-RX5T-QorD-vLsh-hMEv-zxT1Qj
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2016-03-17 09:19:33 +0800
LV Status NOT available
LV Size 1.17 TiB
Current LE 306815
Segments 3
Allocation inherit
Read ahead sectors auto[root@VM001 VolGroup]# lvscan
ACTIVE '/dev/VolGroup/lv_root' [20.00 GiB] inherit
ACTIVE '/dev/VolGroup/lv_swap' [5.00 GiB] inherit
inactive '/dev/VolGroup/lv_home' [1.17 TiB] inherit问题排查：
执行vgdisplay -v命令有2个pv missing信息，此处为关键报错信息：
[root@VM001 ~]# vgdisplay -v
Using volume group(s) on command line.
Finding all volume groups.
Wiping cache of LVM-capable devices
There are 2 physical volumes missing.
There are 2 physical volumes missing.
--- Volume group ---
VG Name VolGroup
System ID
Format lvm2
Metadata Areas 4
...........查看pv状态：
[root@VM001 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/xvda2 VolGroup lvm2 a-m 49.51g 0
/dev/xvda3 VolGroup lvm2 a-m 973.99g 0
/dev/xvde VolGroup lvm2 a-- 200.00g 0
/dev/xvdf1 VolGroup lvm2 a-- 1023.99g 1023.99g查看pvs参数说明：
# man pvs
.......
NOTES
The pv_attr bits are:
1 (d)uplicate, (a)llocatable, (u)sed
2 e(x)ported
3 (m)issing可以确认/dev/xvda2和/dev/xvda3两个物理卷状态为missing(a-m).
问题解决：
用vgextend - -restoremissing命令成功恢复pv到正常状态：
man vgextend有如下说明：
# man vgextend
.......
DESCRIPTION
vgextend adds one or more PVs to a VG. This increases the space available for LVs in the VG.
Also, PVs that have gone missing and then returned, e.g. due to a transient device failure, can be added back to the VG without re-initializing them
(see --restoremissing).
.......
- -restoremissing
Add a PV back into a VG after the PV was missing and then returned, e.g. due to a transient failure. The PV is not reinitialized
# 在PV丢失后再将PV添加到VG中，然后返回，例如由于瞬时故障。没有重新初始化PV。命令格式：
# vgextend VG PV执行命令：
# vgextend --restoremissing VolGroup /dev/xvda2
# vgextend --restoremissing VolGroup /dev/xvda2执行完成以后查看pv状态，已经恢复正常：
[root@VM001 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/xvda2 VolGroup lvm2 a-- 49.51g 0
/dev/xvda3 VolGroup lvm2 a-- 973.99g 0
/dev/xvde VolGroup lvm2 a-- 200.00g 0
/dev/xvdf1 VolGroup lvm2 a-- 1023.99g 1023.99g再查看lv状态，也恢复正常，能够正常挂载并进行扩容：
[root@VM001 ~]# vgdisplay -v
Using volume group(s) on command line.
Finding all volume groups.
--- Volume group ---
VG Name VolGroup
System ID
............
--- Logical volume ---
LV Path /dev/VolGroup/lv_home
LV Name lv_home
VG Name VolGroup
LV UUID 4rdajn-62q9-RX5T-QorD-vLsh-hMEv-zxT1Qj
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2016-03-17 09:19:33 +0800
LV Status available
# open 1
LV Size 2.15 TiB
Current LE 562815
Segments 4
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2 手动执行挂载，此时lv_home逻辑卷挂载恢复正常：
[root@VM001 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
20G 7.3G 12G 40% /
tmpfs 3.9G 224K 3.9G 1% /dev/shm
/dev/xvda1 477M 124M 328M 28% /boot
/dev/mapper/VolGroup-lv_home
2.2T 1.2T 876G 58% /home网上看到的其他类似问题：
案例1：
执行lvextend -l +100%FREE /dev/VolGroup00/LogVol00的时候，出现了如下错误:
Device still marked missing because of allocated data on it, remove volumes and consider bgreduce --removemissing.在查阅许多资料之后，发现可以使用restoremissing 参数来恢复
[root@Caron ~]# vgextend --restoremissing VolGroup00 /dev/sdh1再次执行lvextend命令的时候，提示成功。重新resize一下lvm大小：
[root@Caron ~]# resize2fs /dev/VolGroup00/LogVol00
[root@Caron ~]# df -h | more
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00 936G 612G 283G 69% /
devtmpfs 126G 0 126G 0% /dev
tmpfs 126G 0 126G 0% /dev/shm
tmpfs 126G 4.1G 122G 4% /run
tmpfs 126G 0 126G 0% /sys/fs/cgroup
/dev/sda1 283M 100M 164M 38% /boot
tmpfs 126G 4.1G 122G 4% /run/netns
tmpfs 26G 0 26G 0% /run/user/0案例2:
1.PV丢失的故障处理，手工创建逻辑卷失败，报错显示有PV丢失：
[root@node29archive]# lvcreate -L 1G -n testlv vgcloud
Cannotchange VG vgcloud while PVs are missing.
Considervgreduce --removemissing.2.进一步查看：
[root@node29archive]# pvs
PV VG Fmt Attr PSize PFree
/dev/mapper/mpathbp1 vgcloud lvm2 a-- 1.82t 89.40g
/dev/mapper/mpathbp2 vgcloud lvm2 a-- 1.82t 91.14g
/dev/mapper/mpathbp3 vgcloud lvm2 a-- 1.82t 30.14g
/dev/mapper/mpathbp4 vgcloud lvm2 a-- 1.64t 30.00g
/dev/mapper/mpathcp1 vgcloud lvm2 a-m 1.82t 84.14g
/dev/mapper/mpathcp2 vgcloud lvm2 a-m 1.82t 117.14g
/dev/mapper/mpathcp3 vgcloud lvm2 a-m 1.82t 1.33t
/dev/mapper/mpathcp4 vgcloud lvm2 a-- 1.81t 1.81t
[root@node29archive]# vgs
VG #PV #LV #SN Attr VSize VFree
vgcloud 8 126 0 wz-pn- 14.36t 3.58t其中发现有三个逻辑卷处于missing的状态
3.经过查找资料得知可以使用vgextend –restoremissing操作解决
[root@node26tmp]# vgextend --restoremissing vgcloud /dev/mapper/mpathcp1
Volume group "vgcloud" successfullyextended
[root@node26tmp]# vgextend --restoremissing vgcloud /dev/mapper/mpathcp2
Volume group "vgcloud" successfullyextended
[root@node26tmp]# vgextend --restoremissing vgcloud /dev/mapper/mpathcp3
Volume group "vgcloud" successfullyextended4.再看已经没有missing状态标示了,手工创建逻辑卷
[root@node29archive]# lvcreate -L 1G -n testlv vgcloud
Logical volume "testlv" created