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在生产系统中使用 LVM 务必要注意 lvm metadata 的备份，曾经在京东的时候发生过虚机用了 lvm 的磁盘系统，然后虚机文件 qcow2 突然坏掉了，想尽了办法也无法恢复，这给我们拉响了警钟啊，使用lvm的时候务必要备份分区信息，否则坏的时候就欲哭无泪了。

缺省在 /etc/lvm/backup/ 目录下是最新的备份，同样历史版本都在 /etc/lvm/archive/ 目录下。

先备份

在开始恢复之前，一定先做个备份

cp -pr /etc/lvm /etc/lvm_bkp

然后去看看archive下的备份信息

ls -l /etc/lvm/archive/vg_storage_00*
-rw-------. 1 root root 13722 Oct 28 23:45 /etc/lvm/archive/vg_storage_00419-1760023262.vg
-rw-------. 1 root root 14571 Oct 28 23:52 /etc/lvm/archive/vg_storage_00420-94024216.vg
...
-rw-------. 1 root root 14749 Nov 23 15:11 /etc/lvm/archive/vg_storage_00676-394223172.vg
-rw-------. 1 root root 14733 Nov 23 15:29 /etc/lvm/archive/vg_storage_00677-187019982.vg
#

最坏的情形恢复 pv

警告：这一步只能在 VG 无法正常运行的时候再运行！！！

先说最坏的情形，LVM的建立路径是 pv —> vg —> lv，假设连 pv（物理卷都没了）

我们选择最近的备份，/etc/lvm/archive/vg_storage_00677-187019982.vg

less /etc/lvm/archive/vg_storage_00677-187019982.vg
...
   physical_volumes {
      pv0 {
         id = "BgR0KJ-JClh-T2gS-k6yK-9RGn-B8Ls-LYPQP0"
...

从里面拿到 pv 的 id ，重建 pv

pvcreate --uuid "BgR0KJ-JClh-T2gS-k6yK-9RGn-B8Ls-LYPQP0" \
  --restorefile /etc/lvm/archive/vg_storage_00677-187019982.vg

恢复 VG

如果 vg 是正常的，那么就不用做第二步了，直接从备份中恢复即可，先查看一下


vgcfgrestore --list vg1

File: /etc/lvm/archive/vg1_00000-1238318622.vg
VG name: vg1
Description: Created *before* executing 'vgcreate vg1 /dev/sda6'
Backup Time: Mon Feb 29 10:58:51 2016

File: /etc/lvm/archive/vg1_00001-285796155.vg
VG name: vg1
Description: Created *before* executing 'lvcreate -L 1G -n lv2 vg1'
Backup Time: Mon Feb 29 10:59:23 2016

File: /etc/lvm/archive/vg1_00002-1661997476.vg     ---> just before removal of volume (this is the archive we need)
VG name: vg1
Description: Created *before* executing 'lvremove /dev/vg1/lv2'
Backup Time: Mon Feb 29 13:55:08 2016

File: /etc/lvm/backup/vg1
VG name: vg1
Description: Created *after* executing 'lvremove /dev/vg1/lv2' 
Backup Time: Mon Feb 29 13:55:08 2016

有信息，我们先加 –test 测试一下


vgcfgrestore vg01 --test -f /etc/lvm/archive/vg_data_00003-586203914.vg

   TEST MODE: Metadata will NOT be updated and volumes will not be (de)activated.
   Volume group vg01 has active volume: lv001.
   WARNING: Found 1 active volume(s) in volume group "vg01".
   Restoring VG with active LVs, may cause mismatch with its metadata.
 Do you really want to proceed with restore of volume group "vg01", while 1 volume(s) are active? [y/n]: y
   Restored volume group vg01.

没问题，那就继续，真的操作了


vgcfgrestore vg01 -f /etc/lvm/archive/vg_data_00003-586203914.vg

   Volume group vg01 has active volume: lv001.
   WARNING: Found 1 active volume(s) in volume group "vg01".
   Restoring VG with active LVs, may cause mismatch with its metadata.
 Do you really want to proceed with restore of volume group "vg01", while 1 volume(s) are active? [y/n]: y
   Restored volume group vg01.

恢复后进行校验


# 显示信息
vgdisplay VG1

# 激活
vgchange -ay VG1

# 显示逻辑卷
lvs -a -o +devices

# 重新扫描
lvscan
inactive '/dev/vg1/lv2' [1.00 GiB] inherit      ### its in inactive state and make it active to use.
ACTIVE '/dev/vg0/lv1' [1.00 GiB] inherit

# 上面如果有inactive的，重新激活
lvchange -a y /dev/vg1/lv2

# 再显示一次
lvs -a -o +devices

# 再扫描
lvscan
ACTIVE '/dev/vg1/lv2' [1.00 GiB] inherit
ACTIVE '/dev/vg0/lv1' [1.00 GiB] inherit

# mount上测试
mount /dev/vg1/lv2 /lv2

# 看看东西都在不在
ls -lh /lv2

备份和恢复的脚本

备份一个 VG 下所有卷，每个卷一个 snapshot 快照备份文件，backup_snapshot_lvm.pl


#!/usr/bin/perl -w
#
# Run through a particular LVM volume group and perform a snapshot
# and compressed file backup of each volume.
#
# This script is intended for use with backing up complete system
# images of VMs, in addition to data level backups.
#

my $source_lvm_volgroup = 'vg_storage';
my $source_lvm_snapsize = '5G';
my @source_lvm_excludes = ('lv_unwanted', 'lv_tmpfiles');

my $dest_dir='/mnt/backup/snapshots';

foreach $volume (glob("/dev/$source_lvm_volgroup/*"))
{
    $volume            =~ /\/dev\/$source_lvm_volgroup\/(\S*)$/;
    my $volume_short    = $1;

    if ("$volume_short" ~~ @source_lvm_excludes)
    {
        # Excluded volume, we skip it
        print "[info] Skipping excluded volume $volume_short ($volume)\n";
        next;
    }

    print "[info] Processing volume $volume_short ($volume)\n";

    # Snapshot volume
    print "[info] Creating snapshot...\n";
    system("lvcreate -n ${volume_short}_snapshot --snapshot $volume -L $source_lvm_snapsize");

    # Write compressed backup file from snapshot, but only replace existing one once finished
    print "[info] Creating compressed snapshot file...\n";
    system("dd if=${volume}_snapshot | gzip --fast > $dest_dir/$volume_short.temp.gz");
    system("mv $dest_dir/$volume_short.temp.gz $dest_dir/$volume_short.gz");

    # Delete snapshot
    print "[info] Removing snapshot...\n";
    system("lvremove --force ${volume}_snapshot");

    print "[info] Volume $volume_short backup completed.\n";
}

print "[info] FINISHED! VolumeGroup backup completed\n";

exit 0;

恢复的脚本，restore_snapshot_lvm.pl：


#!/usr/bin/perl -w
#
# Runs through LVM snapshots taken by backup_snapshot_lvm.pl and
# restores them to the LVM volume in question.
#

my $dest_lvm_volgroup = 'vg_storage';
my $source_dir = '/mnt/backup/snapshots';

print "[WARNING] Beginning restore process in 5 SECONDS!!\n";
sleep(5);

foreach $volume (glob("$source_dir/*"))
{
    $volume            =~ /$source_dir\/(\S*).gz$/;
    my $volume_short    = $1;

    print "[info] Processing volume $volume_short ($volume)\n";

    # Just need to decompress & write into LVM volume
    system("zcat $source_dir/$volume_short.gz > /dev/$dest_lvm_volgroup/$volume_short");

    print "[info] Volume $volume_short restore completed.\n";
}

print "[info] FINISHED! VolumeGroup restore completed\n";

exit 0;

当然要谨记，这个是块设备级别的备份，最好还是要有另外的数据的备份。

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