记录一个问题的处理过程：
环境：suse 9,oracle 9,外接一个存储用于备份；

发现/backup目录下为空，但是又可看到该目录
ciqhist:/ # df -lh
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3             320G  290G   15G  96% /
tmpfs                 7.9G  8.0K  7.9G   1% /dev/shm
/dev/sda1             198M   11M  177M   6% /boot
/dev/mapper/backupvg-backuplv    790G  642G  108G  86% /backup

ciqhist:/ # mount
/dev/sda3 on / type ext3 (rw,acl,user_xattr)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
tmpfs on /dev/shm type tmpfs (rw)
devpts on /dev/pts type devpts (rw,mode=0620,gid=5)
/dev/sda1 on /boot type ext3 (rw,acl,user_xattr)
/dev/hda on /media/dvd type subfs (ro,nosuid,nodev,fs=cdfss,procuid,iocharset=utf8)
usbfs on /proc/bus/usb type usbfs (rw)
nfsd on /proc/fs/nfsd type nfsd (rw)
/dev/mapper/backupvg-backuplv on /backup type ext3 (rw)

尝试先umount该/backup,
# umount /backup
失败，报 device is busy
同时通过fdisk -l查看磁盘，发现没有挂载lvm磁盘；
怀疑是存储断掉了；

强制kill掉访问该目录的进程
ciqhist:/ # fuser -km /backup
/backup:             30478 30482
再umount该目录，成功
 ciqhist:/ # umount /backup

经现场人员确认，存储前段时间关掉，刚启动存储。

关闭数据库，重启服务器；
重启服务器后，
fdisk -l 查看存储已经可以识别到了；
挂载该目录还是报错
ciqhist:/ # mount /dev/mapper/backupvg-backuplv /backup
/dev/mapper/backupvg-backuplv: Inappropriate ioctl for device
mount: /dev/mapper/backupvg-backuplv: can't read superblock

查看本机发现没有vg 和 lv
重新扫描

ciqhist:~ # pvscan
  PV /dev/sdb1   VG backupvg   lvm2 [801.88 GB / 80.00 MB free]
  Total: 1 [801.88 GB] / in use: 1 [801.88 GB] / in no VG: 0 [0   ]
ciqhist:~ # vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "backupvg" using metadata type lvm2
ciqhist:~ # lvscan
  inactive          '/dev/backupvg/backuplv' [801.80 GB] inherit

ciqhist:~ # pvs
  PV         VG       Fmt  Attr PSize   PFree
  /dev/sdb1  backupvg lvm2 a-   801.88G 80.00M
ciqhist:~ # lvs
  LV       VG       Attr   LSize   Origin Snap%  Move Log Copy%
  backuplv backupvg -wi--- 801.80G                              
ciqhist:~ # vgs
  VG       #PV #LV #SN Attr  VSize   VFree
  backupvg   1   1   0 wz--n 801.88G 80.00M

mount依然报错
ciqhist:~ # mount -t ext3 /dev/mapper/backupvg-backuplv /backup
mount: /dev/mapper/backupvg-backuplv is not a valid block device

激活该vg
ciqhist:~ # vgchange -a y
  1 logical volume(s) in volume group "backupvg" now active
ciqhist:~ # lvs
  LV       VG       Attr   LSize   Origin Snap%  Move Log Copy%
  backuplv backupvg -wi-a- 801.80G                              
ciqhist:~ # lvscan
  ACTIVE            '/dev/backupvg/backuplv' [801.80 GB] inherit
ciqhist:~ # mount -t ext3 /dev/mapper/backupvg-backuplv /backup
挂载成功。


lvm管理激活参考：http://ljx198308.blog.163.com/blog/static/1762742462011292134116/