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diff --git a/Documentation/ldm.txt b/Documentation/ldm.txt new file mode 100644 index 000000000..4f80edd14 --- /dev/null +++ b/Documentation/ldm.txt @@ -0,0 +1,109 @@ + + LDM - Logical Disk Manager (Dynamic Disks) + ------------------------------------------ + +Originally Written by FlatCap - Richard Russon <ldm@flatcap.org>. +Last Updated by Anton Altaparmakov on 30 March 2007 for Windows Vista. + +Overview +-------- + +Windows 2000, XP, and Vista 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. This is what is +supported with the Linux LDM driver. + +A newer approach that has been implemented with Vista is to put LDM on top of a +GPT label disk. This is not supported by the Linux LDM driver yet. + + +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 together with complete Technical Documentation. +It is available for download. + + http://www.linux-ntfs.org/ + +If you have any LDM questions that aren't answered in the documentation, email +me. + +Cheers, + FlatCap - Richard Russon + ldm@flatcap.org + |