| 1 | ==========================================
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| 2 | LDM - Logical Disk Manager (Dynamic Disks)
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| 3 | ==========================================
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| 4 |
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| 5 | :Author: Originally Written by FlatCap - Richard Russon <[email protected]>.
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| 6 | :Last Updated: Anton Altaparmakov on 30 March 2007 for Windows Vista.
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| 7 |
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| 8 | Overview
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| 9 | --------
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| 10 |
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| 11 | Windows 2000, XP, and Vista use a new partitioning scheme. It is a complete
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| 12 | replacement for the MSDOS style partitions. It stores its information in a
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| 13 | 1MiB journalled database at the end of the physical disk. The size of
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| 14 | partitions is limited only by disk space. The maximum number of partitions is
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| 15 | nearly 2000.
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| 16 |
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| 17 | Any partitions created under the LDM are called "Dynamic Disks". There are no
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| 18 | longer any primary or extended partitions. Normal MSDOS style partitions are
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| 19 | now known as Basic Disks.
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| 20 |
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| 21 | If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
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| 22 | Dynamic Disks. The journalling allows Windows to make changes to these
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| 23 | partitions and filesystems without the need to reboot.
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| 24 |
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| 25 | Once the LDM driver has divided up the disk, you can use the MD driver to
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| 26 | assemble any multi-partition volumes, e.g. Stripes, RAID5.
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| 27 |
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| 28 | To prevent legacy applications from repartitioning the disk, the LDM creates a
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| 29 | dummy MSDOS partition containing one disk-sized partition. This is what is
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| 30 | supported with the Linux LDM driver.
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| 31 |
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| 32 | A newer approach that has been implemented with Vista is to put LDM on top of a
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| 33 | GPT label disk. This is not supported by the Linux LDM driver yet.
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| 34 |
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| 35 |
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| 36 | Example
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| 37 | -------
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| 38 |
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| 39 | Below we have a 50MiB disk, divided into seven partitions.
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| 40 |
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| 41 | .. note::
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| 42 |
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| 43 | The missing 1MiB at the end of the disk is where the LDM database is
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| 44 | stored.
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| 45 |
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| 46 | +-------++--------------+---------+-----++--------------+---------+----+
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| 47 | |Device || Offset Bytes | Sectors | MiB || Size Bytes | Sectors | MiB|
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| 48 | +=======++==============+=========+=====++==============+=========+====+
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| 49 | |hda || 0 | 0 | 0 || 52428800 | 102400 | 50|
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| 50 | +-------++--------------+---------+-----++--------------+---------+----+
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| 51 | |hda1 || 51380224 | 100352 | 49 || 1048576 | 2048 | 1|
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| 52 | +-------++--------------+---------+-----++--------------+---------+----+
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| 53 | |hda2 || 16384 | 32 | 0 || 6979584 | 13632 | 6|
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| 54 | +-------++--------------+---------+-----++--------------+---------+----+
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| 55 | |hda3 || 6995968 | 13664 | 6 || 10485760 | 20480 | 10|
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| 56 | +-------++--------------+---------+-----++--------------+---------+----+
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| 57 | |hda4 || 17481728 | 34144 | 16 || 4194304 | 8192 | 4|
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| 58 | +-------++--------------+---------+-----++--------------+---------+----+
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| 59 | |hda5 || 21676032 | 42336 | 20 || 5242880 | 10240 | 5|
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| 60 | +-------++--------------+---------+-----++--------------+---------+----+
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| 61 | |hda6 || 26918912 | 52576 | 25 || 10485760 | 20480 | 10|
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| 62 | +-------++--------------+---------+-----++--------------+---------+----+
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| 63 | |hda7 || 37404672 | 73056 | 35 || 13959168 | 27264 | 13|
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| 64 | +-------++--------------+---------+-----++--------------+---------+----+
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| 65 |
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| 66 | The LDM Database may not store the partitions in the order that they appear on
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| 67 | disk, but the driver will sort them.
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| 68 |
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| 69 | When Linux boots, you will see something like::
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| 70 |
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| 71 | hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
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| 72 | hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
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| 73 |
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| 74 |
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| 75 | Compiling LDM Support
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| 76 | ---------------------
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| 77 |
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| 78 | To enable LDM, choose the following two options:
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| 79 |
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| 80 | - "Advanced partition selection" CONFIG_PARTITION_ADVANCED
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| 81 | - "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
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| 82 |
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| 83 | If you believe the driver isn't working as it should, you can enable the extra
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| 84 | debugging code. This will produce a LOT of output. The option is:
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| 85 |
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| 86 | - "Windows LDM extra logging" CONFIG_LDM_DEBUG
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| 87 |
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| 88 | N.B. The partition code cannot be compiled as a module.
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| 89 |
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| 90 | As with all the partition code, if the driver doesn't see signs of its type of
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| 91 | partition, it will pass control to another driver, so there is no harm in
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| 92 | enabling it.
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| 93 |
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| 94 | If you have Dynamic Disks but don't enable the driver, then all you will see
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| 95 | is a dummy MSDOS partition filling the whole disk. You won't be able to mount
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| 96 | any of the volumes on the disk.
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| 97 |
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| 98 |
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| 99 | Booting
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| 100 | -------
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| 101 |
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| 102 | If you enable LDM support, then lilo is capable of booting from any of the
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| 103 | discovered partitions. However, grub does not understand the LDM partitioning
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| 104 | and cannot boot from a Dynamic Disk.
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| 105 |
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| 106 |
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| 107 | More Documentation
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| 108 | ------------------
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| 109 |
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| 110 | There is an Overview of the LDM together with complete Technical Documentation.
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| 111 | It is available for download.
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| 112 |
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| 113 | http://www.linux-ntfs.org/
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| 114 |
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| 115 | If you have any LDM questions that aren't answered in the documentation, email
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| 116 | me.
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| 117 |
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| 118 | Cheers,
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| 119 | FlatCap - Richard Russon
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| 120 | [email protected]
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| 121 |
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