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| LDM - Logical Disk Manager (Dynamic Disks) |
| ------------------------------------------ |
| |
| Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>. |
| Last Updated by 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. |
| N.B. 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: |
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| "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/content/view/19/37/ |
| |
| If you have any LDM questions that aren't answered in the documentation, email |
| me. |
| |
| Cheers, |
| FlatCap - Richard Russon |
| ldm@flatcap.org |
| |