| ========================================== | |
| 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 | |