ldm.txt 3.6 KB

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