ntfs.txt

linux 内核源代码

You will need to create a table of the components of the volume/stripe set and
how they fit together and load this into the kernel using the dmsetup utility
(see man 8 dmsetup).

Linear volume sets, i.e. linear raid, has been tested and works fine.  Even
though untested, there is no reason why stripe sets, i.e. raid level 0, and
mirrors, i.e. raid level 1 should not work, too.  Stripes with parity, i.e.
raid level 5, unfortunately cannot work yet because the current version of the
Device-Mapper driver does not support raid level 5.  You may be able to use the
Software RAID / MD driver for raid level 5, see the next section for details.

To create the table describing your volume you will need to know each of its
components and their sizes in sectors, i.e. multiples of 512-byte blocks.

For NT4 fault tolerant volumes you can obtain the sizes using fdisk.  So for
example if one of your partitions is /dev/hda2 you would do:

$ fdisk -ul /dev/hda

Disk /dev/hda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors
Units = sectors of 1 * 512 = 512 bytes

   Device Boot      Start         End      Blocks   Id  System
   /dev/hda1   *          63     4209029     2104483+  83  Linux
   /dev/hda2         4209030    37768814    16779892+  86  NTFS
   /dev/hda3        37768815    46170809     4200997+  83  Linux

And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 =
33559785 sectors.

For Win2k and later dynamic disks, you can for example use the ldminfo utility
which is part of the Linux LDM tools (the latest version at the time of
writing is linux-ldm-0.0.8.tar.bz2).  You can download it from:
	http://linux-ntfs.sourceforge.net/downloads.html
Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go
into it (cd linux-ldm-0.0.8) and change to the test directory (cd test).  You
will find the precompiled (i386) ldminfo utility there.  NOTE: You will not be
able to compile this yourself easily so use the binary version!

Then you would use ldminfo in dump mode to obtain the necessary information:

$ ./ldminfo --dump /dev/hda

This would dump the LDM database found on /dev/hda which describes all of your
dynamic disks and all the volumes on them.  At the bottom you will see the
VOLUME DEFINITIONS section which is all you really need.  You may need to look
further above to determine which of the disks in the volume definitions is
which device in Linux.  Hint: Run ldminfo on each of your dynamic disks and
look at the Disk Id close to the top of the output for each (the PRIVATE HEADER
section).  You can then find these Disk Ids in the VBLK DATABASE section in the
<Disk> components where you will get the LDM Name for the disk that is found in
the VOLUME DEFINITIONS section.

Note you will also need to enable the LDM driver in the Linux kernel.  If your
distribution did not enable it, you will need to recompile the kernel with it
enabled.  This will create the LDM partitions on each device at boot time.  You
would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc)
in the Device-Mapper table.

You can also bypass using the LDM driver by using the main device (e.g.
/dev/hda) and then using the offsets of the LDM partitions into this device as
the "Start sector of device" when creating the table.  Once again ldminfo would
give you the correct information to do this.

Assuming you know all your devices and their sizes things are easy.

For a linear raid the table would look like this (note all values are in
512-byte sectors):

--- cut here ---
# Offset into	Size of this	Raid type	Device		Start sector
# volume	device						of device
0		1028161		linear		/dev/hda1	0
1028161		3903762		linear		/dev/hdb2	0
4931923		2103211		linear		/dev/hdc1	0
--- cut here ---

For a striped volume, i.e. raid level 0, you will need to know the chunk size
you used when creating the volume.  Windows uses 64kiB as the default, so it
will probably be this unless you changes the defaults when creating the array.

For a raid level 0 the table would look like this (note all values are in
512-byte sectors):

--- cut here ---
# Offset   Size	    Raid     Number   Chunk  1st        Start	2nd	  Start
# into     of the   type     of	      size   Device	in	Device	  in
# volume   volume	     stripes			device		  device
0	   2056320  striped  2	      128    /dev/hda1	0	/dev/hdb1 0
--- cut here ---

If there are more than two devices, just add each of them to the end of the
line.

Finally, for a mirrored volume, i.e. raid level 1, the table would look like
this (note all values are in 512-byte sectors):

--- cut here ---
# Ofs Size   Raid   Log  Number Region Should Number Source  Start Target Start
# in  of the type   type of log size   sync?  of     Device  in    Device in
# vol volume		 params		     mirrors	     Device	  Device
0    2056320 mirror core 2	16     nosync 2	   /dev/hda1 0   /dev/hdb1 0
--- cut here ---

If you are mirroring to multiple devices you can specify further targets at the
end of the line.

Note the "Should sync?" parameter "nosync" means that the two mirrors are
already in sync which will be the case on a clean shutdown of Windows.  If the
mirrors are not clean, you can specify the "sync" option instead of "nosync"
and the Device-Mapper driver will then copy the entirety of the "Source Device"
to the "Target Device" or if you specified multipled target devices to all of
them.

Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1),
and hand it over to dmsetup to work with, like so:

$ dmsetup create myvolume1 /etc/ntfsvolume1

You can obviously replace "myvolume1" with whatever name you like.

If it all worked, you will now have the device /dev/device-mapper/myvolume1
which you can then just use as an argument to the mount command as usual to
mount the ntfs volume.  For example:

$ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1

(You need to create the directory /mnt/myvol1 first and of course you can use
anything you like instead of /mnt/myvol1 as long as it is an existing
directory.)

It is advisable to do the mount read-only to see if the volume has been setup
correctly to avoid the possibility of causing damage to the data on the ntfs
volume.


The Software RAID / MD driver
-----------------------------

An alternative to using the Device-Mapper driver is to use the kernel's
Software RAID / MD driver.  For which you need to set up your /etc/raidtab
appropriately (see man 5 raidtab).

Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level
0, have been tested and work fine (though see section "Limitations when using
the MD driver with NTFS volumes" especially if you want to use linear raid).
Even though untested, there is no reason why mirrors, i.e. raid level 1, and
stripes with parity, i.e. raid level 5, should not work, too.

You have to use the "persistent-superblock 0" option for each raid-disk in the
NTFS volume/stripe you are configuring in /etc/raidtab as the persistent
superblock used by the MD driver would damage the NTFS volume.

Windows by default uses a stripe chunk size of 64k, so you probably want the
"chunk-size 64k" option for each raid-disk, too.

For example, if you have a stripe set consisting of two partitions /dev/hda5
and /dev/hdb1 your /etc/raidtab would look like this:

raiddev /dev/md0
	raid-level	0
	nr-raid-disks	2
	nr-spare-disks	0
	persistent-superblock	0
	chunk-size	64k
	device		/dev/hda5
	raid-disk	0
	device		/dev/hdb1
	raid-disk	1

For linear raid, just change the raid-level above to "raid-level linear", for
mirrors, change it to "raid-level 1", and for stripe sets with parity, change
it to "raid-level 5".

Note for stripe sets with parity you will also need to tell the MD driver
which parity algorithm to use by specifying the option "parity-algorithm
which", where you need to replace "which" with the name of the algorithm to
use (see man 5 raidtab for available algorithms) and you will have to try the
different available algorithms until you find one that works.  Make sure you
are working read-only when playing with this as you may damage your data
otherwise.  If you find which algorithm works please let us know (email the
linux-ntfs developers list [e-mail] or drop in on
IRC in channel #ntfs on the irc.freenode.net network) so we can update this
documentation.

Once the raidtab is setup, run for example raid0run -a to start all devices or
raid0run /dev/md0 to start a particular md device, in this case /dev/md0.

Then just use the mount command as usual to mount the ntfs volume using for
example:	mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume

It is advisable to do the mount read-only to see if the md volume has been
setup correctly to avoid the possibility of causing damage to the data on the
ntfs volume.


Limitations when using the Software RAID / MD driver
-----------------------------------------------------

Using the md driver will not work properly if any of your NTFS partitions have
an odd number of sectors.  This is especially important for linear raid as all
data after the first partition with an odd number of sectors will be offset by
one or more sectors so if you mount such a partition with write support you
will cause massive damage to the data on the volume which will only become
apparent when you try to use the volume again under Windows.

So when using linear raid, make sure that all your partitions have an even
number of sectors BEFORE attempting to use it.  You have been warned!

Even better is to simply use the Device-Mapper for linear raid and then you do
not have this problem with odd numbers of sectors.


ChangeLog
=========

Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.

2.1.29:
	- Fix a deadlock when mounting read-write.
2.1.28:
	- Fix a deadlock.
2.1.27:
	- Implement page migration support so the kernel can move memory used
	  by NTFS files and directories around for management purposes.
	- Add support for writing to sparse files created with Windows XP SP2.
	- Many minor improvements and bug fixes.
2.1.26:
	- Implement support for sector sizes above 512 bytes (up to the maximum
	  supported by NTFS which is 4096 bytes).
	- Enhance support for NTFS volumes which were supported by Windows but
	  not by Linux due to invalid attribute list attribute flags.
	- A few minor updates and bug fixes.
2.1.25:
	- Write support is now extended with write(2) being able to both
	  overwrite existing file data and to extend files.  Also, if a write
	  to a sparse region occurs, write(2) will fill in the hole.  Note,