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1da177e4 LT |
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 |