linux/Documentation/ldm.txt
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   2            LDM - Logical Disk Manager (Dynamic Disks)
   3            ------------------------------------------
   4
   5Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>.
   6Last Updated by Anton Altaparmakov on 30 March 2007 for Windows Vista.
   7
   8Overview
   9--------
  10
  11Windows 2000, XP, and Vista use a new partitioning scheme.  It is a complete
  12replacement for the MSDOS style partitions.  It stores its information in a
  131MiB journalled database at the end of the physical disk.  The size of
  14partitions is limited only by disk space.  The maximum number of partitions is
  15nearly 2000.
  16
  17Any partitions created under the LDM are called "Dynamic Disks".  There are no
  18longer any primary or extended partitions.  Normal MSDOS style partitions are
  19now known as Basic Disks.
  20
  21If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
  22Dynamic Disks.  The journalling allows Windows to make changes to these
  23partitions and filesystems without the need to reboot.
  24
  25Once the LDM driver has divided up the disk, you can use the MD driver to
  26assemble any multi-partition volumes, e.g.  Stripes, RAID5.
  27
  28To prevent legacy applications from repartitioning the disk, the LDM creates a
  29dummy MSDOS partition containing one disk-sized partition.  This is what is
  30supported with the Linux LDM driver.
  31
  32A newer approach that has been implemented with Vista is to put LDM on top of a
  33GPT label disk.  This is not supported by the Linux LDM driver yet.
  34
  35
  36Example
  37-------
  38
  39Below we have a 50MiB disk, divided into seven partitions.
  40N.B.  The missing 1MiB at the end of the disk is where the LDM database is
  41      stored.
  42
  43  Device | Offset Bytes  Sectors  MiB | Size   Bytes  Sectors  MiB
  44  -------+----------------------------+---------------------------
  45  hda    |            0        0    0 |     52428800   102400   50
  46  hda1   |     51380224   100352   49 |      1048576     2048    1
  47  hda2   |        16384       32    0 |      6979584    13632    6
  48  hda3   |      6995968    13664    6 |     10485760    20480   10
  49  hda4   |     17481728    34144   16 |      4194304     8192    4
  50  hda5   |     21676032    42336   20 |      5242880    10240    5
  51  hda6   |     26918912    52576   25 |     10485760    20480   10
  52  hda7   |     37404672    73056   35 |     13959168    27264   13
  53
  54The LDM Database may not store the partitions in the order that they appear on
  55disk, but the driver will sort them.
  56
  57When Linux boots, you will see something like:
  58
  59  hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
  60  hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
  61
  62
  63Compiling LDM Support
  64---------------------
  65
  66To enable LDM, choose the following two options: 
  67
  68  "Advanced partition selection" CONFIG_PARTITION_ADVANCED
  69  "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
  70
  71If you believe the driver isn't working as it should, you can enable the extra
  72debugging code.  This will produce a LOT of output.  The option is:
  73
  74  "Windows LDM extra logging" CONFIG_LDM_DEBUG
  75
  76N.B. The partition code cannot be compiled as a module.
  77
  78As with all the partition code, if the driver doesn't see signs of its type of
  79partition, it will pass control to another driver, so there is no harm in
  80enabling it.
  81
  82If you have Dynamic Disks but don't enable the driver, then all you will see
  83is a dummy MSDOS partition filling the whole disk.  You won't be able to mount
  84any of the volumes on the disk.
  85
  86
  87Booting
  88-------
  89
  90If you enable LDM support, then lilo is capable of booting from any of the
  91discovered partitions.  However, grub does not understand the LDM partitioning
  92and cannot boot from a Dynamic Disk.
  93
  94
  95More Documentation
  96------------------
  97
  98There is an Overview of the LDM together with complete Technical Documentation.
  99It is available for download.
 100
 101  http://www.linux-ntfs.org/content/view/19/37/
 102
 103If you have any LDM questions that aren't answered in the documentation, email
 104me.
 105
 106Cheers,
 107    FlatCap - Richard Russon
 108    ldm@flatcap.org
 109
 110
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