6.2. 从 LVM 镜像故障中恢复
本节提供了从 LVM 镜像卷的一个 leg 失败时恢复的示例，因为物理卷的底层设备停机，
mirror_log_fault_policy 参数被设置为 删除。这要求您手动重建镜像。有关设置 mirror_log_fault_policy 参数的详情，请参考 第 4.4.4.1 节 “镜像逻辑卷失败策略”。
当镜像分支失败时，LVM 会将镜像卷转换为线性卷，它仍象以前运行，但没有镜像冗余。此时，您可以向系统添加新磁盘设备，以用作替换物理设备并重新构建镜像。
以下命令创建了用于镜像的物理卷。
# pvcreate /dev/sd[abcdefgh][12]
Physical volume "/dev/sda1" successfully created
Physical volume "/dev/sda2" successfully created
Physical volume "/dev/sdb1" successfully created
Physical volume "/dev/sdb2" successfully created
Physical volume "/dev/sdc1" successfully created
Physical volume "/dev/sdc2" successfully created
Physical volume "/dev/sdd1" successfully created
Physical volume "/dev/sdd2" successfully created
Physical volume "/dev/sde1" successfully created
Physical volume "/dev/sde2" successfully created
Physical volume "/dev/sdf1" successfully created
Physical volume "/dev/sdf2" successfully created
Physical volume "/dev/sdg1" successfully created
Physical volume "/dev/sdg2" successfully created
Physical volume "/dev/sdh1" successfully created
Physical volume "/dev/sdh2" successfully created
以下命令创建卷组
vg 和镜像卷组 groupfs。
#vgcreate vg /dev/sd[abcdefgh][12]Volume group "vg" successfully created #lvcreate -L 750M -n groupfs -m 1 vg /dev/sda1 /dev/sdb1 /dev/sdc1Rounding up size to full physical extent 752.00 MB Logical volume "groupfs" created
您可以使用 lvs 命令验证镜像卷的布局，以及镜像 leg 和镜像日志的底层设备。请注意，在第一个示例中，镜像还没有完全同步；您应该等到
Copy% 字段显示 100.00，然后再继续。
#lvs -a -o +devicesLV VG Attr LSize Origin Snap% Move Log Copy% Devices groupfs vg mwi-a- 752.00M groupfs_mlog 21.28 groupfs_mimage_0(0),groupfs_mimage_1(0) [groupfs_mimage_0] vg iwi-ao 752.00M /dev/sda1(0) [groupfs_mimage_1] vg iwi-ao 752.00M /dev/sdb1(0) [groupfs_mlog] vg lwi-ao 4.00M /dev/sdc1(0) #lvs -a -o +devicesLV VG Attr LSize Origin Snap% Move Log Copy% Devices groupfs vg mwi-a- 752.00M groupfs_mlog 100.00 groupfs_mimage_0(0),groupfs_mimage_1(0) [groupfs_mimage_0] vg iwi-ao 752.00M /dev/sda1(0) [groupfs_mimage_1] vg iwi-ao 752.00M /dev/sdb1(0) [groupfs_mlog] vg lwi-ao 4.00M i /dev/sdc1(0)
在这个示例中，镜像
/dev/sda1 的主要 leg 失败。任何对镜像卷的写操作会导致 LVM 检测到失败的镜像。当发生这种情况时，LVM 将镜像转换为单一线性卷。在这种情况下，要触发转换，我们执行一个 dd 命令
# dd if=/dev/zero of=/dev/vg/groupfs count=10
10+0 records in
10+0 records out
您可以使用 lvs 命令验证该设备现在是否为线性设备。由于磁盘失败，所以会出现 I/O 错误。
# lvs -a -o +devices
/dev/sda1: read failed after 0 of 2048 at 0: Input/output error
LV VG Attr LSize Origin Snap% Move Log Copy% Devices
groupfs vg -wi-a- 752.00M /dev/sdb1(0)
此时，您仍然能够使用逻辑卷，但没有镜像冗余功能。
要重建镜像的卷，替换有问题的驱动器并重新创建物理卷。如果您使用同一磁盘而不是将其替换为新磁盘，则在运行 pvcreate 命令时会看到"不一致"警告。您可以通过执行 vgreduce --removemissing 命令来防止显示该警告。
#pvcreate /dev/sdi[12]Physical volume "/dev/sdi1" successfully created Physical volume "/dev/sdi2" successfully created #pvscanPV /dev/sdb1 VG vg lvm2 [67.83 GB / 67.10 GB free] PV /dev/sdb2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdc1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdc2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdd1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdd2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sde1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sde2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdf1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdf2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdg1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdg2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdh1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdh2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdi1 lvm2 [603.94 GB] PV /dev/sdi2 lvm2 [603.94 GB] Total: 16 [2.11 TB] / in use: 14 [949.65 GB] / in no VG: 2 [1.18 TB]
然后使用新物理卷扩展原始卷组。
#vgextend vg /dev/sdi[12]Volume group "vg" successfully extended #pvscanPV /dev/sdb1 VG vg lvm2 [67.83 GB / 67.10 GB free] PV /dev/sdb2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdc1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdc2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdd1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdd2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sde1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sde2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdf1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdf2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdg1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdg2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdh1 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdh2 VG vg lvm2 [67.83 GB / 67.83 GB free] PV /dev/sdi1 VG vg lvm2 [603.93 GB / 603.93 GB free] PV /dev/sdi2 VG vg lvm2 [603.93 GB / 603.93 GB free] Total: 16 [2.11 TB] / in use: 16 [2.11 TB] / in no VG: 0 [0 ]
将线性卷重新转换为其原始镜像状态。
# lvconvert -m 1 /dev/vg/groupfs /dev/sdi1 /dev/sdb1 /dev/sdc1
Logical volume mirror converted.
您可以使用 lvs 命令验证镜像是否已恢复。
# lvs -a -o +devices
LV VG Attr LSize Origin Snap% Move Log Copy% Devices
groupfs vg mwi-a- 752.00M groupfs_mlog 68.62 groupfs_mimage_0(0),groupfs_mimage_1(0)
[groupfs_mimage_0] vg iwi-ao 752.00M /dev/sdb1(0)
[groupfs_mimage_1] vg iwi-ao 752.00M /dev/sdi1(0)
[groupfs_mlog] vg lwi-ao 4.00M /dev/sdc1(0)
