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