ldm.rst 4.6 KB

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  1. ==========================================
  2. LDM - Logical Disk Manager (Dynamic Disks)
  3. ==========================================
  4. :Author: Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>.
  5. :Last Updated: Anton Altaparmakov on 30 March 2007 for Windows Vista.
  6. Overview
  7. --------
  8. Windows 2000, XP, and Vista use a new partitioning scheme. It is a complete
  9. replacement for the MSDOS style partitions. It stores its information in a
  10. 1MiB journalled database at the end of the physical disk. The size of
  11. partitions is limited only by disk space. The maximum number of partitions is
  12. nearly 2000.
  13. Any partitions created under the LDM are called "Dynamic Disks". There are no
  14. longer any primary or extended partitions. Normal MSDOS style partitions are
  15. now known as Basic Disks.
  16. If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
  17. Dynamic Disks. The journalling allows Windows to make changes to these
  18. partitions and filesystems without the need to reboot.
  19. Once the LDM driver has divided up the disk, you can use the MD driver to
  20. assemble any multi-partition volumes, e.g. Stripes, RAID5.
  21. To prevent legacy applications from repartitioning the disk, the LDM creates a
  22. dummy MSDOS partition containing one disk-sized partition. This is what is
  23. supported with the Linux LDM driver.
  24. A newer approach that has been implemented with Vista is to put LDM on top of a
  25. GPT label disk. This is not supported by the Linux LDM driver yet.
  26. Example
  27. -------
  28. Below we have a 50MiB disk, divided into seven partitions.
  29. .. note::
  30. The missing 1MiB at the end of the disk is where the LDM database is
  31. stored.
  32. +-------++--------------+---------+-----++--------------+---------+----+
  33. |Device || Offset Bytes | Sectors | MiB || Size Bytes | Sectors | MiB|
  34. +=======++==============+=========+=====++==============+=========+====+
  35. |hda || 0 | 0 | 0 || 52428800 | 102400 | 50|
  36. +-------++--------------+---------+-----++--------------+---------+----+
  37. |hda1 || 51380224 | 100352 | 49 || 1048576 | 2048 | 1|
  38. +-------++--------------+---------+-----++--------------+---------+----+
  39. |hda2 || 16384 | 32 | 0 || 6979584 | 13632 | 6|
  40. +-------++--------------+---------+-----++--------------+---------+----+
  41. |hda3 || 6995968 | 13664 | 6 || 10485760 | 20480 | 10|
  42. +-------++--------------+---------+-----++--------------+---------+----+
  43. |hda4 || 17481728 | 34144 | 16 || 4194304 | 8192 | 4|
  44. +-------++--------------+---------+-----++--------------+---------+----+
  45. |hda5 || 21676032 | 42336 | 20 || 5242880 | 10240 | 5|
  46. +-------++--------------+---------+-----++--------------+---------+----+
  47. |hda6 || 26918912 | 52576 | 25 || 10485760 | 20480 | 10|
  48. +-------++--------------+---------+-----++--------------+---------+----+
  49. |hda7 || 37404672 | 73056 | 35 || 13959168 | 27264 | 13|
  50. +-------++--------------+---------+-----++--------------+---------+----+
  51. The LDM Database may not store the partitions in the order that they appear on
  52. disk, but the driver will sort them.
  53. When Linux boots, you will see something like::
  54. hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
  55. hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
  56. Compiling LDM Support
  57. ---------------------
  58. To enable LDM, choose the following two options:
  59. - "Advanced partition selection" CONFIG_PARTITION_ADVANCED
  60. - "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
  61. If you believe the driver isn't working as it should, you can enable the extra
  62. debugging code. This will produce a LOT of output. The option is:
  63. - "Windows LDM extra logging" CONFIG_LDM_DEBUG
  64. N.B. The partition code cannot be compiled as a module.
  65. As with all the partition code, if the driver doesn't see signs of its type of
  66. partition, it will pass control to another driver, so there is no harm in
  67. enabling it.
  68. If you have Dynamic Disks but don't enable the driver, then all you will see
  69. is a dummy MSDOS partition filling the whole disk. You won't be able to mount
  70. any of the volumes on the disk.
  71. Booting
  72. -------
  73. If you enable LDM support, then lilo is capable of booting from any of the
  74. discovered partitions. However, grub does not understand the LDM partitioning
  75. and cannot boot from a Dynamic Disk.
  76. More Documentation
  77. ------------------
  78. There is an Overview of the LDM together with complete Technical Documentation.
  79. It is available for download.
  80. http://www.linux-ntfs.org/
  81. If you have any LDM questions that aren't answered in the documentation, email
  82. me.
  83. Cheers,
  84. FlatCap - Richard Russon
  85. ldm@flatcap.org