122 lines
4.6 KiB
ReStructuredText
122 lines
4.6 KiB
ReStructuredText
==========================================
|
|
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
|
|
|