Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/ldm.txt
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Tag kernel26-2.6.12-alx-r9
1 | |
2 | LDM - Logical Disk Manager (Dynamic Disks) |
3 | ------------------------------------------ |
4 | |
5 | Overview |
6 | -------- |
7 | |
8 | Windows 2000 and XP use a new partitioning scheme. It is a complete |
9 | replacement for the MSDOS style partitions. It stores its information in a |
10 | 1MiB journalled database at the end of the physical disk. The size of |
11 | partitions is limited only by disk space. The maximum number of partitions is |
12 | nearly 2000. |
13 | |
14 | Any partitions created under the LDM are called "Dynamic Disks". There are no |
15 | longer any primary or extended partitions. Normal MSDOS style partitions are |
16 | now known as Basic Disks. |
17 | |
18 | If you wish to use Spanned, Striped, Mirrored or RAID 5 Volumes, you must use |
19 | Dynamic Disks. The journalling allows Windows to make changes to these |
20 | partitions and filesystems without the need to reboot. |
21 | |
22 | Once the LDM driver has divided up the disk, you can use the MD driver to |
23 | assemble any multi-partition volumes, e.g. Stripes, RAID5. |
24 | |
25 | To prevent legacy applications from repartitioning the disk, the LDM creates a |
26 | dummy MSDOS partition containing one disk-sized partition. |
27 | |
28 | |
29 | Example |
30 | ------- |
31 | |
32 | Below we have a 50MiB disk, divided into seven partitions. |
33 | N.B. The missing 1MiB at the end of the disk is where the LDM database is |
34 | stored. |
35 | |
36 | Device | Offset Bytes Sectors MiB | Size Bytes Sectors MiB |
37 | -------+----------------------------+--------------------------- |
38 | hda | 0 0 0 | 52428800 102400 50 |
39 | hda1 | 51380224 100352 49 | 1048576 2048 1 |
40 | hda2 | 16384 32 0 | 6979584 13632 6 |
41 | hda3 | 6995968 13664 6 | 10485760 20480 10 |
42 | hda4 | 17481728 34144 16 | 4194304 8192 4 |
43 | hda5 | 21676032 42336 20 | 5242880 10240 5 |
44 | hda6 | 26918912 52576 25 | 10485760 20480 10 |
45 | hda7 | 37404672 73056 35 | 13959168 27264 13 |
46 | |
47 | The LDM Database may not store the partitions in the order that they appear on |
48 | disk, but the driver will sort them. |
49 | |
50 | When Linux boots, you will see something like: |
51 | |
52 | hda: 102400 sectors w/32KiB Cache, CHS=50/64/32 |
53 | hda: [LDM] hda1 hda2 hda3 hda4 hda5 hda6 hda7 |
54 | |
55 | |
56 | Compiling LDM Support |
57 | --------------------- |
58 | |
59 | To enable LDM, choose the following two options: |
60 | |
61 | "Advanced partition selection" CONFIG_PARTITION_ADVANCED |
62 | "Windows Logical Disk Manager (Dynamic Disk) support" CONFIG_LDM_PARTITION |
63 | |
64 | If you believe the driver isn't working as it should, you can enable the extra |
65 | debugging code. This will produce a LOT of output. The option is: |
66 | |
67 | "Windows LDM extra logging" CONFIG_LDM_DEBUG |
68 | |
69 | N.B. The partition code cannot be compiled as a module. |
70 | |
71 | As with all the partition code, if the driver doesn't see signs of its type of |
72 | partition, it will pass control to another driver, so there is no harm in |
73 | enabling it. |
74 | |
75 | If you have Dynamic Disks but don't enable the driver, then all you will see |
76 | is a dummy MSDOS partition filling the whole disk. You won't be able to mount |
77 | any of the volumes on the disk. |
78 | |
79 | |
80 | Booting |
81 | ------- |
82 | |
83 | If you enable LDM support, then lilo is capable of booting from any of the |
84 | discovered partitions. However, grub does not understand the LDM partitioning |
85 | and cannot boot from a Dynamic Disk. |
86 | |
87 | |
88 | More Documentation |
89 | ------------------ |
90 | |
91 | There is an Overview of the LDM online together with complete Technical |
92 | Documentation. It can also be downloaded in html. |
93 | |
94 | http://linux-ntfs.sourceforge.net/ldm/index.html |
95 | http://linux-ntfs.sourceforge.net/downloads.html |
96 | |
97 | If you have any LDM questions that aren't answered on the website, email me. |
98 | |
99 | Cheers, |
100 | FlatCap - Richard Russon |
101 | ldm@flatcap.org |
102 |