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0001 
0002             LDM - Logical Disk Manager (Dynamic Disks)
0003             ------------------------------------------
0004 
0005 Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>.
0006 Last Updated by Anton Altaparmakov on 30 March 2007 for Windows Vista.
0007 
0008 Overview
0009 --------
0010 
0011 Windows 2000, XP, and Vista use a new partitioning scheme.  It is a complete
0012 replacement for the MSDOS style partitions.  It stores its information in a
0013 1MiB journalled database at the end of the physical disk.  The size of
0014 partitions is limited only by disk space.  The maximum number of partitions is
0015 nearly 2000.
0016 
0017 Any partitions created under the LDM are called "Dynamic Disks".  There are no
0018 longer any primary or extended partitions.  Normal MSDOS style partitions are
0019 now known as Basic Disks.
0020 
0021 If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
0022 Dynamic Disks.  The journalling allows Windows to make changes to these
0023 partitions and filesystems without the need to reboot.
0024 
0025 Once the LDM driver has divided up the disk, you can use the MD driver to
0026 assemble any multi-partition volumes, e.g.  Stripes, RAID5.
0027 
0028 To prevent legacy applications from repartitioning the disk, the LDM creates a
0029 dummy MSDOS partition containing one disk-sized partition.  This is what is
0030 supported with the Linux LDM driver.
0031 
0032 A newer approach that has been implemented with Vista is to put LDM on top of a
0033 GPT label disk.  This is not supported by the Linux LDM driver yet.
0034 
0035 
0036 Example
0037 -------
0038 
0039 Below we have a 50MiB disk, divided into seven partitions.
0040 N.B.  The missing 1MiB at the end of the disk is where the LDM database is
0041       stored.
0042 
0043   Device | Offset Bytes  Sectors  MiB | Size   Bytes  Sectors  MiB
0044   -------+----------------------------+---------------------------
0045   hda    |            0        0    0 |     52428800   102400   50
0046   hda1   |     51380224   100352   49 |      1048576     2048    1
0047   hda2   |        16384       32    0 |      6979584    13632    6
0048   hda3   |      6995968    13664    6 |     10485760    20480   10
0049   hda4   |     17481728    34144   16 |      4194304     8192    4
0050   hda5   |     21676032    42336   20 |      5242880    10240    5
0051   hda6   |     26918912    52576   25 |     10485760    20480   10
0052   hda7   |     37404672    73056   35 |     13959168    27264   13
0053 
0054 The LDM Database may not store the partitions in the order that they appear on
0055 disk, but the driver will sort them.
0056 
0057 When Linux boots, you will see something like:
0058 
0059   hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
0060   hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
0061 
0062 
0063 Compiling LDM Support
0064 ---------------------
0065 
0066 To enable LDM, choose the following two options: 
0067 
0068   "Advanced partition selection" CONFIG_PARTITION_ADVANCED
0069   "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
0070 
0071 If you believe the driver isn't working as it should, you can enable the extra
0072 debugging code.  This will produce a LOT of output.  The option is:
0073 
0074   "Windows LDM extra logging" CONFIG_LDM_DEBUG
0075 
0076 N.B. The partition code cannot be compiled as a module.
0077 
0078 As with all the partition code, if the driver doesn't see signs of its type of
0079 partition, it will pass control to another driver, so there is no harm in
0080 enabling it.
0081 
0082 If you have Dynamic Disks but don't enable the driver, then all you will see
0083 is a dummy MSDOS partition filling the whole disk.  You won't be able to mount
0084 any of the volumes on the disk.
0085 
0086 
0087 Booting
0088 -------
0089 
0090 If you enable LDM support, then lilo is capable of booting from any of the
0091 discovered partitions.  However, grub does not understand the LDM partitioning
0092 and cannot boot from a Dynamic Disk.
0093 
0094 
0095 More Documentation
0096 ------------------
0097 
0098 There is an Overview of the LDM together with complete Technical Documentation.
0099 It is available for download.
0100 
0101   http://www.linux-ntfs.org/
0102 
0103 If you have any LDM questions that aren't answered in the documentation, email
0104 me.
0105 
0106 Cheers,
0107     FlatCap - Richard Russon
0108     ldm@flatcap.org
0109