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Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 12 years 9 months ago. By Lars-Peter Clausen, jz4740: Fix compile error | |
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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/ |
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 | |
110 |
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