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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/ldm.txt
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+
+ LDM - Logical Disk Manager (Dynamic Disks)
+ ------------------------------------------
+
+Overview
+--------
+
+Windows 2000 and XP 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.
+
+
+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:
+
+ "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 online together with complete Technical
+Documentation. It can also be downloaded in html.
+
+ http://linux-ntfs.sourceforge.net/ldm/index.html
+ http://linux-ntfs.sourceforge.net/downloads.html
+
+If you have any LDM questions that aren't answered on the website, email me.
+
+Cheers,
+ FlatCap - Richard Russon
+ ldm@flatcap.org
+

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