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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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+==========================================
+LDM - Logical Disk Manager (Dynamic Disks)
+==========================================
+
+:Author: Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>.
+:Last Updated: Anton Altaparmakov on 30 March 2007 for Windows Vista.
+
+Overview
+--------
+
+Windows 2000, XP, and Vista use a new partitioning scheme. It is a complete
+replacement for the MSDOS style partitions. It stores its information in a
+1MiB journalled database at the end of the physical disk. The size of
+partitions is limited only by disk space. The maximum number of partitions is
+nearly 2000.
+
+Any partitions created under the LDM are called "Dynamic Disks". There are no
+longer any primary or extended partitions. Normal MSDOS style partitions are
+now known as Basic Disks.
+
+If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use
+Dynamic Disks. The journalling allows Windows to make changes to these
+partitions and filesystems without the need to reboot.
+
+Once the LDM driver has divided up the disk, you can use the MD driver to
+assemble any multi-partition volumes, e.g. Stripes, RAID5.
+
+To prevent legacy applications from repartitioning the disk, the LDM creates a
+dummy MSDOS partition containing one disk-sized partition. This is what is
+supported with the Linux LDM driver.
+
+A newer approach that has been implemented with Vista is to put LDM on top of a
+GPT label disk. This is not supported by the Linux LDM driver yet.
+
+
+Example
+-------
+
+Below we have a 50MiB disk, divided into seven partitions.
+
+.. note::
+
+ The missing 1MiB at the end of the disk is where the LDM database is
+ stored.
+
++-------++--------------+---------+-----++--------------+---------+----+
+|Device || Offset Bytes | Sectors | MiB || Size Bytes | Sectors | MiB|
++=======++==============+=========+=====++==============+=========+====+
+|hda || 0 | 0 | 0 || 52428800 | 102400 | 50|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda1 || 51380224 | 100352 | 49 || 1048576 | 2048 | 1|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda2 || 16384 | 32 | 0 || 6979584 | 13632 | 6|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda3 || 6995968 | 13664 | 6 || 10485760 | 20480 | 10|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda4 || 17481728 | 34144 | 16 || 4194304 | 8192 | 4|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda5 || 21676032 | 42336 | 20 || 5242880 | 10240 | 5|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda6 || 26918912 | 52576 | 25 || 10485760 | 20480 | 10|
++-------++--------------+---------+-----++--------------+---------+----+
+|hda7 || 37404672 | 73056 | 35 || 13959168 | 27264 | 13|
++-------++--------------+---------+-----++--------------+---------+----+
+
+The LDM Database may not store the partitions in the order that they appear on
+disk, but the driver will sort them.
+
+When Linux boots, you will see something like::
+
+ hda: 102400 sectors w/32KiB Cache, CHS=50/64/32
+ hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7
+
+
+Compiling LDM Support
+---------------------
+
+To enable LDM, choose the following two options:
+
+ - "Advanced partition selection" CONFIG_PARTITION_ADVANCED
+ - "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION
+
+If you believe the driver isn't working as it should, you can enable the extra
+debugging code. This will produce a LOT of output. The option is:
+
+ - "Windows LDM extra logging" CONFIG_LDM_DEBUG
+
+N.B. The partition code cannot be compiled as a module.
+
+As with all the partition code, if the driver doesn't see signs of its type of
+partition, it will pass control to another driver, so there is no harm in
+enabling it.
+
+If you have Dynamic Disks but don't enable the driver, then all you will see
+is a dummy MSDOS partition filling the whole disk. You won't be able to mount
+any of the volumes on the disk.
+
+
+Booting
+-------
+
+If you enable LDM support, then lilo is capable of booting from any of the
+discovered partitions. However, grub does not understand the LDM partitioning
+and cannot boot from a Dynamic Disk.
+
+
+More Documentation
+------------------
+
+There is an Overview of the LDM together with complete Technical Documentation.
+It is available for download.
+
+ http://www.linux-ntfs.org/
+
+If you have any LDM questions that aren't answered in the documentation, email
+me.
+
+Cheers,
+ FlatCap - Richard Russon
+ ldm@flatcap.org
+