LDM & ldmtool

在Windows系统中创建了一个带区动态卷，其实就是用两个磁盘以RAID0方式整合也一个大磁盘。但启动进入Ubuntu (14.04) 系统后并不能正确识别。下图是我在测试系统中创建了一个带区卷E:（由2个盘构成）和一个RAID5卷F:（由4个盘构成）：

这两个由Windows系统创建的动态卷，是LDM格式（Logical Disk Manager），Linux系统中不能正确识别。最初我尝试用mdadm强制加载带区卷，分别试了64K及128K chunk，但全部无效，尝试办法如下：
root@ubuntu:~# mdadm --build /dev/md0 --level=0 --chunk=128 --raid-devices=2 /dev/sd[cd]3
mdadm: array /dev/md0 built and started.
root@ubuntu:~# mdadm --detail /dev/md0
/dev/md0:
        Version :
  Creation Time : Thu Jun 25 16:08:11 2015
     Raid Level : raid0
     Array Size : 41680640 (39.75 GiB 42.68 GB)
   Raid Devices : 2
  Total Devices : 2

          State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
  Spare Devices : 0

     Chunk Size : 128K

    Number   Major   Minor   RaidDevice State
       0       8       35        0      active sync   /dev/sdc3
       1       8       51        1      active sync   /dev/sdd3
root@ubuntu:~# tune2fs -l /dev/md0
tune2fs 1.42.9 (4-Feb-2014)
tune2fs: Bad magic number in super-block while trying to open /dev/md0
Couldn't find valid filesystem superblock.
root@ubuntu:~# mdadm -S /dev/md0
mdadm: stopped /dev/md0
root@ubuntu:~# mdadm --build /dev/md0 --level=0 --chunk=128 --raid-devices=2 /dev/sd[dc]3
mdadm: array /dev/md0 built and started.
root@ubuntu:~# mdadm --detail /dev/md0
/dev/md0:
        Version :
  Creation Time : Thu Jun 25 16:08:57 2015
     Raid Level : raid0
     Array Size : 41680640 (39.75 GiB 42.68 GB)
   Raid Devices : 2
  Total Devices : 2

          State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
  Spare Devices : 0

     Chunk Size : 128K

    Number   Major   Minor   RaidDevice State
       0       8       51        0      active sync   /dev/sdd3
       1       8       35        1      active sync   /dev/sdc3
root@ubuntu:~# tune2fs -l /dev/md0
tune2fs 1.42.9 (4-Feb-2014)
tune2fs: Bad magic number in super-block while trying to open /dev/md0
Couldn't find valid filesystem superblock.
root@ubuntu:~# mdadm -S /dev/md0
mdadm: stopped /dev/md0
root@ubuntu:~#

后来几经搜索，发现解决方案原来很简单，只需要安装ldmtool。

root@ubuntu:~# parted -l
Model: VMware, VMware Virtual S (scsi)
Disk /dev/sda: 85.9GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system     Flags
1      1049kB  1000MB  999MB   primary  ext2            boot
2      1000MB  81.0GB  80.0GB  primary  xfs
3      81.0GB  85.9GB  4898MB  primary  linux-swap(v1)

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdb: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
1      1049kB  42.9GB  42.9GB  primary  ext4

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdc: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   21.5GB  21.3GB               LDM data partition

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdd: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   21.5GB  21.3GB               LDM data partition

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sde: 64.4GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   64.4GB  64.3GB               LDM data partition

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdf: 64.4GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   64.4GB  64.3GB               LDM data partition

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdg: 64.4GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   64.4GB  64.3GB               LDM data partition

Model: VMware, VMware Virtual S (scsi)
Disk /dev/sdh: 64.4GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                          Flags
1      17.4kB  1066kB  1049kB               LDM metadata partition
2      1066kB  134MB   133MB                Microsoft reserved partition  msftres
3      134MB   64.4GB  64.3GB               LDM data partition

root@ubuntu:~# ldmtool scan
[
  "3ffea520-1b24-11e5-8565-000c293dbd64"
]
root@ubuntu:~# ldmtool show diskgroup 3ffea520-1b24-11e5-8565-000c293dbd64
{
  "name" : "WIN-FB20IXK90MU-Dg0",
  "guid" : "3ffea520-1b24-11e5-8565-000c293dbd64",
  "volumes" : [
    "Volume2",
    "Volume1"
  ],
  "disks" : [
    "Disk1",
    "Disk2",
    "Disk3",
    "Disk4",
    "Disk6",
    "Disk5"
  ]
}
root@ubuntu:~# ldmtool show volume 3ffea520-1b24-11e5-8565-000c293dbd64 Volume1
{
  "name" : "Volume1",
  "type" : "RAID5",
  "size" : 376688640,
  "chunk-size" : 128,
  "hint" : "F:",
  "partitions" : [
    "Disk1-01",
    "Disk2-01",
    "Disk3-01",
    "Disk4-01"
  ]
}
root@ubuntu:~# ldmtool show volume 3ffea520-1b24-11e5-8565-000c293dbd64 Volume2
{
  "name" : "Volume2",
  "type" : "striped",
  "size" : 83353600,
  "chunk-size" : 128,
  "hint" : "E:",
  "partitions" : [
    "Disk5-01",
    "Disk6-01"
  ]
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk1-01
{
  "name" : "Disk1-01",
  "start" : 2014,
  "size" : 125562880,
  "disk" : "Disk1"
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk2-01
{
  "name" : "Disk2-01",
  "start" : 2014,
  "size" : 125562880,
  "disk" : "Disk2"
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk3-01
{
  "name" : "Disk3-01",
  "start" : 2014,
  "size" : 125562880,
  "disk" : "Disk3"
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk4-01
{
  "name" : "Disk4-01",
  "start" : 2014,
  "size" : 125562880,
  "disk" : "Disk4"
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk5-01
{
  "name" : "Disk5-01",
  "start" : 2014,
  "size" : 41676800,
  "disk" : "Disk5"
}
root@ubuntu:~# ldmtool show partition 3ffea520-1b24-11e5-8565-000c293dbd64 Disk6-01
{
  "name" : "Disk6-01",
  "start" : 2014,
  "size" : 41676800,
  "disk" : "Disk6"
}

用ldmtool解析并创建动态卷只需要一个简单命令：

root@ubuntu:~# ldmtool create all
[
  "ldm_vol_WIN-FB20IXK90MU-Dg0_Volume2",
  "ldm_vol_WIN-FB20IXK90MU-Dg0_Volume1"
]

root@ubuntu:~# ls -l /dev/mapper/
total 0
crw------- 1 root root 10, 236 Jun 25 16:29 control
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_part_WIN-FB20IXK90MU-Dg0_Disk1-01 -> ../dm-1
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_part_WIN-FB20IXK90MU-Dg0_Disk2-01 -> ../dm-2
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_part_WIN-FB20IXK90MU-Dg0_Disk3-01 -> ../dm-3
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_part_WIN-FB20IXK90MU-Dg0_Disk4-01 -> ../dm-4
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_vol_WIN-FB20IXK90MU-Dg0_Volume1 -> ../dm-5
lrwxrwxrwx 1 root root       7 Jun 25 16:29 ldm_vol_WIN-FB20IXK90MU-Dg0_Volume2 -> ../dm-0

root@ubuntu:~# ls -l /dev/dm*
brw-rw---- 1 root disk 252, 0 Jun 25 16:29 /dev/dm-0
brw-rw---- 1 root disk 252, 1 Jun 25 16:29 /dev/dm-1
brw-rw---- 1 root disk 252, 2 Jun 25 16:29 /dev/dm-2
brw-rw---- 1 root disk 252, 3 Jun 25 16:29 /dev/dm-3
brw-rw---- 1 root disk 252, 4 Jun 25 16:29 /dev/dm-4
brw-rw---- 1 root disk 252, 5 Jun 25 16:29 /dev/dm-5
root@ubuntu:~#
root@ubuntu:~# tune2fs -l /dev/dm-0
tune2fs 1.42.9 (4-Feb-2014)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          22a45231-ede2-4c60-9c93-ee841ae2f2ee
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex
_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              2605056
Block count:              10419200
Reserved block count:     520960
Free blocks:              10210674
Free inodes:              2605045
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      1021
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8192
Inode blocks per group:   512
RAID stride:              16
RAID stripe width:        32
Flex block group size:    16
Filesystem created:       Thu Jun 25 15:58:29 2015
Last mount time:          n/a
Last write time:          Thu Jun 25 15:58:31 2015
Mount count:              0
Maximum mount count:      -1
Last checked:             Thu Jun 25 15:58:29 2015
Check interval:           0 (<none>)
Lifetime writes:          132 MB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               256
Required extra isize:     28
Desired extra isize:      28
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      a472f2f6-a27b-4362-91e2-dce4ad48a700
Journal backup:           inode blocks
root@ubuntu:~# tune2fs -l /dev/dm-5
tune2fs 1.42.9 (4-Feb-2014)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          f0655359-b2e0-4732-8df0-b0ab24918ec1
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex
_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              11771904
Block count:              47086080
Reserved block count:     2354304
Free blocks:              46299313
Free inodes:              11771893
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      1012
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8192
Inode blocks per group:   512
RAID stride:              16
RAID stripe width:        48
Flex block group size:    16
Filesystem created:       Thu Jun 25 15:13:55 2015
Last mount time:          n/a
Last write time:          Thu Jun 25 15:14:21 2015
Mount count:              6
Maximum mount count:      -1
Last checked:             Thu Jun 25 15:14:21 2015
Check interval:           0 (<none>)
Lifetime writes:          133 MB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               256
Required extra isize:     28
Desired extra isize:      28
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      88ddd8a2-506a-4e9b-9109-ce9c171b2607
Journal backup:           inode blocks

至此就可以自由访问 /dev/dm-0和/dev/dm-5两个设备卷了。不过还要说的是，ldmtool是通过DM (Device Mapper) 产生的RAID卷（和LVM使用的是同样的机制），而不是最常用的MD方式(即Multiple Devices)，特别对于RAID5/RAID6此类的数据卷，MD Raid做了较多的优化，除性能更好之外，稳定性应该也好于Device Mapper方式。

参考阅读：
1，http://manpages.ubuntu.com/manpages/trusty/man1/ldmtool.1.html
2，https://github.com/mdbooth/libldm
3，https://notesbytom.wordpress.com/2012/06/14/linux-support-for-windows-dynamic-disks/
4，http://stackoverflow.com/questions/8427372/windows-spanned-disks-ldm-restoration-with-linux/22108676#22108676 <ldmtool出现之前的办法 >