Documentation/filesystems/ntfs.txt - kernel/msm-4.19 - Gitiles

 The Linux NTFS filesystem driver
 ================================


 Table of contents
 =================

 - Overview
 - Web site
 - Features
 - Supported mount options
 - Known bugs and (mis-)features
 - Using NTFS volume and stripe sets
   - The Device-Mapper driver
   - The Software RAID / MD driver
   - Limitations when using the MD driver


 Overview
 ========

 Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
 These include mkntfs, a full-featured ntfs filesystem format utility,
 ntfsundelete used for recovering files that were unintentionally deleted
 from an NTFS volume and ntfsresize which is used to resize an NTFS partition.
 See the web site for more information.

 To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file
 system type 'ntfs'.  The driver currently supports read-only mode (with no
 fault-tolerance, encryption or journalling) and very limited, but safe, write
 support.

 For fault tolerance and raid support (i.e. volume and stripe sets), you can
 use the kernel's Software RAID / MD driver.  See section "Using Software RAID
 with NTFS" for details.


 Web site
 ========

 There is plenty of additional information on the linux-ntfs web site
 at http://www.linux-ntfs.org/

 The web site has a lot of additional information, such as a comprehensive
 FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS
 userspace utilities, etc.


 Features
 ========

 - This is a complete rewrite of the NTFS driver that used to be in the 2.4 and
   earlier kernels.  This new driver implements NTFS read support and is
   functionally equivalent to the old ntfs driver and it also implements limited
   write support.  The biggest limitation at present is that files/directories
   cannot be created or deleted.  See below for the list of write features that
   are so far supported.  Another limitation is that writing to compressed files
   is not implemented at all.  Also, neither read nor write access to encrypted
   files is so far implemented.
 - The new driver has full support for sparse files on NTFS 3.x volumes which
   the old driver isn't happy with.
 - The new driver supports execution of binaries due to mmap() now being
   supported.
 - The new driver supports loopback mounting of files on NTFS which is used by
   some Linux distributions to enable the user to run Linux from an NTFS
   partition by creating a large file while in Windows and then loopback
   mounting the file while in Linux and creating a Linux filesystem on it that
   is used to install Linux on it.
 - A comparison of the two drivers using:
 	time find . -type f -exec md5sum "{}" \;
   run three times in sequence with each driver (after a reboot) on a 1.4GiB
   NTFS partition, showed the new driver to be 20% faster in total time elapsed
   (from 9:43 minutes on average down to 7:53).  The time spent in user space
   was unchanged but the time spent in the kernel was decreased by a factor of
   2.5 (from 85 CPU seconds down to 33).
 - The driver does not support short file names in general.  For backwards
   compatibility, we implement access to files using their short file names if
   they exist.  The driver will not create short file names however, and a
   rename will discard any existing short file name.
 - The new driver supports exporting of mounted NTFS volumes via NFS.
 - The new driver supports async io (aio).
 - The new driver supports fsync(2), fdatasync(2), and msync(2).
 - The new driver supports readv(2) and writev(2).
 - The new driver supports access time updates (including mtime and ctime).
 - The new driver supports truncate(2) and open(2) with O_TRUNC.  But at present
   only very limited support for highly fragmented files, i.e. ones which have
   their data attribute split across multiple extents, is included.  Another
   limitation is that at present truncate(2) will never create sparse files,
   since to mark a file sparse we need to modify the directory entry for the
   file and we do not implement directory modifications yet.
 - The new driver supports write(2) which can both overwrite existing data and
   extend the file size so that you can write beyond the existing data.  Also,
   writing into sparse regions is supported and the holes are filled in with
   clusters.  But at present only limited support for highly fragmented files,
   i.e. ones which have their data attribute split across multiple extents, is
   included.  Another limitation is that write(2) will never create sparse
   files, since to mark a file sparse we need to modify the directory entry for
   the file and we do not implement directory modifications yet.

 Supported mount options
 =======================

 In addition to the generic mount options described by the manual page for the
 mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the
 following mount options:

 iocharset=name		Deprecated option.  Still supported but please use
 			nls=name in the future.  See description for nls=name.

 nls=name		Character set to use when returning file names.
 			Unlike VFAT, NTFS suppresses names that contain
 			unconvertible characters.  Note that most character
 			sets contain insufficient characters to represent all
 			possible Unicode characters that can exist on NTFS.
 			To be sure you are not missing any files, you are
 			advised to use nls=utf8 which is capable of
 			representing all Unicode characters.

 utf8=<bool>		Option no longer supported.  Currently mapped to
 			nls=utf8 but please use nls=utf8 in the future and
 			make sure utf8 is compiled either as module or into
 			the kernel.  See description for nls=name.

 uid=
 gid=
 umask=			Provide default owner, group, and access mode mask.
 			These options work as documented in mount(8).  By
 			default, the files/directories are owned by root and
 			he/she has read and write permissions, as well as
 			browse permission for directories.  No one else has any
 			access permissions.  I.e. the mode on all files is by
 			default rw------- and for directories rwx------, a
 			consequence of the default fmask=0177 and dmask=0077.
 			Using a umask of zero will grant all permissions to
 			everyone, i.e. all files and directories will have mode
 			rwxrwxrwx.

 fmask=
 dmask=			Instead of specifying umask which applies both to
 			files and directories, fmask applies only to files and
 			dmask only to directories.

 sloppy=<BOOL>		If sloppy is specified, ignore unknown mount options.
 			Otherwise the default behaviour is to abort mount if
 			any unknown options are found.

 show_sys_files=<BOOL>	If show_sys_files is specified, show the system files
 			in directory listings.  Otherwise the default behaviour
 			is to hide the system files.
 			Note that even when show_sys_files is specified, "$MFT"
 			will not be visible due to bugs/mis-features in glibc.
 			Further, note that irrespective of show_sys_files, all
 			files are accessible by name, i.e. you can always do
 			"ls -l \$UpCase" for example to specifically show the
 			system file containing the Unicode upcase table.

 case_sensitive=<BOOL>	If case_sensitive is specified, treat all file names as
 			case sensitive and create file names in the POSIX
 			namespace.  Otherwise the default behaviour is to treat
 			file names as case insensitive and to create file names
 			in the WIN32/LONG name space.  Note, the Linux NTFS
 			driver will never create short file names and will
 			remove them on rename/delete of the corresponding long
 			file name.
 			Note that files remain accessible via their short file
 			name, if it exists.  If case_sensitive, you will need
 			to provide the correct case of the short file name.

 disable_sparse=<BOOL>	If disable_sparse is specified, creation of sparse
 			regions, i.e. holes, inside files is disabled for the
 			volume (for the duration of this mount only).  By
 			default, creation of sparse regions is enabled, which
 			is consistent with the behaviour of traditional Unix
 			filesystems.

 errors=opt		What to do when critical filesystem errors are found.
 			Following values can be used for "opt":
 			  continue: DEFAULT, try to clean-up as much as
 				    possible, e.g. marking a corrupt inode as
 				    bad so it is no longer accessed, and then
 				    continue.
 			  recover:  At present only supported is recovery of
 				    the boot sector from the backup copy.
 				    If read-only mount, the recovery is done
 				    in memory only and not written to disk.
 			Note that the options are additive, i.e. specifying:
 			   errors=continue,errors=recover
 			means the driver will attempt to recover and if that
 			fails it will clean-up as much as possible and
 			continue.

 mft_zone_multiplier=	Set the MFT zone multiplier for the volume (this
 			setting is not persistent across mounts and can be
 			changed from mount to mount but cannot be changed on
 			remount).  Values of 1 to 4 are allowed, 1 being the
 			default.  The MFT zone multiplier determines how much
 			space is reserved for the MFT on the volume.  If all
 			other space is used up, then the MFT zone will be
 			shrunk dynamically, so this has no impact on the
 			amount of free space.  However, it can have an impact
 			on performance by affecting fragmentation of the MFT.
 			In general use the default.  If you have a lot of small
 			files then use a higher value.  The values have the
 			following meaning:
 			      Value	     MFT zone size (% of volume size)
 				1		12.5%
 				2		25%
 				3		37.5%
 				4		50%
 			Note this option is irrelevant for read-only mounts.


 Known bugs and (mis-)features
 =============================

 - The link count on each directory inode entry is set to 1, due to Linux not
   supporting directory hard links.  This may well confuse some user space
   applications, since the directory names will have the same inode numbers.
   This also speeds up ntfs_read_inode() immensely.  And we haven't found any
   problems with this approach so far.  If you find a problem with this, please
   let us know.


 Please send bug reports/comments/feedback/abuse to the Linux-NTFS development
 list at sourceforge: linux-ntfs-dev@lists.sourceforge.net


 Using NTFS volume and stripe sets
 =================================

 For support of volume and stripe sets, you can either use the kernel's
 Device-Mapper driver or the kernel's Software RAID / MD driver.  The former is
 the recommended one to use for linear raid.  But the latter is required for
 raid level 5.  For striping and mirroring, either driver should work fine.


 The Device-Mapper driver
 ------------------------

 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://www.linux-ntfs.org/
 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 multiple 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 linux-ntfs-dev@lists.sourceforge.net 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.
	The Linux NTFS filesystem driver
	================================


	Table of contents
	=================

	- Overview
	- Web site
	- Features
	- Supported mount options
	- Known bugs and (mis-)features
	- Using NTFS volume and stripe sets
	- The Device-Mapper driver
	- The Software RAID / MD driver
	- Limitations when using the MD driver


	Overview
	========

	Linux-NTFS comes with a number of user-space programs known as ntfsprogs.
	These include mkntfs, a full-featured ntfs filesystem format utility,
	ntfsundelete used for recovering files that were unintentionally deleted
	from an NTFS volume and ntfsresize which is used to resize an NTFS partition.
	See the web site for more information.

	To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file
	system type 'ntfs'. The driver currently supports read-only mode (with no
	fault-tolerance, encryption or journalling) and very limited, but safe, write
	support.

	For fault tolerance and raid support (i.e. volume and stripe sets), you can
	use the kernel's Software RAID / MD driver. See section "Using Software RAID
	with NTFS" for details.


	Web site
	========

	There is plenty of additional information on the linux-ntfs web site
	at http://www.linux-ntfs.org/

	The web site has a lot of additional information, such as a comprehensive
	FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS
	userspace utilities, etc.


	Features
	========

	- This is a complete rewrite of the NTFS driver that used to be in the 2.4 and
	earlier kernels. This new driver implements NTFS read support and is
	functionally equivalent to the old ntfs driver and it also implements limited
	write support. The biggest limitation at present is that files/directories
	cannot be created or deleted. See below for the list of write features that
	are so far supported. Another limitation is that writing to compressed files
	is not implemented at all. Also, neither read nor write access to encrypted
	files is so far implemented.
	- The new driver has full support for sparse files on NTFS 3.x volumes which
	the old driver isn't happy with.
	- The new driver supports execution of binaries due to mmap() now being
	supported.
	- The new driver supports loopback mounting of files on NTFS which is used by
	some Linux distributions to enable the user to run Linux from an NTFS
	partition by creating a large file while in Windows and then loopback
	mounting the file while in Linux and creating a Linux filesystem on it that
	is used to install Linux on it.
	- A comparison of the two drivers using:
	time find . -type f -exec md5sum "{}" \;
	run three times in sequence with each driver (after a reboot) on a 1.4GiB
	NTFS partition, showed the new driver to be 20% faster in total time elapsed
	(from 9:43 minutes on average down to 7:53). The time spent in user space
	was unchanged but the time spent in the kernel was decreased by a factor of
	2.5 (from 85 CPU seconds down to 33).
	- The driver does not support short file names in general. For backwards
	compatibility, we implement access to files using their short file names if
	they exist. The driver will not create short file names however, and a
	rename will discard any existing short file name.
	- The new driver supports exporting of mounted NTFS volumes via NFS.
	- The new driver supports async io (aio).
	- The new driver supports fsync(2), fdatasync(2), and msync(2).
	- The new driver supports readv(2) and writev(2).
	- The new driver supports access time updates (including mtime and ctime).
	- The new driver supports truncate(2) and open(2) with O_TRUNC. But at present
	only very limited support for highly fragmented files, i.e. ones which have
	their data attribute split across multiple extents, is included. Another
	limitation is that at present truncate(2) will never create sparse files,
	since to mark a file sparse we need to modify the directory entry for the
	file and we do not implement directory modifications yet.
	- The new driver supports write(2) which can both overwrite existing data and
	extend the file size so that you can write beyond the existing data. Also,
	writing into sparse regions is supported and the holes are filled in with
	clusters. But at present only limited support for highly fragmented files,
	i.e. ones which have their data attribute split across multiple extents, is
	included. Another limitation is that write(2) will never create sparse
	files, since to mark a file sparse we need to modify the directory entry for
	the file and we do not implement directory modifications yet.

	Supported mount options
	=======================

	In addition to the generic mount options described by the manual page for the
	mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the
	following mount options:

	iocharset=name Deprecated option. Still supported but please use
	nls=name in the future. See description for nls=name.

	nls=name Character set to use when returning file names.
	Unlike VFAT, NTFS suppresses names that contain
	unconvertible characters. Note that most character
	sets contain insufficient characters to represent all
	possible Unicode characters that can exist on NTFS.
	To be sure you are not missing any files, you are
	advised to use nls=utf8 which is capable of
	representing all Unicode characters.

	utf8=<bool> Option no longer supported. Currently mapped to
	nls=utf8 but please use nls=utf8 in the future and
	make sure utf8 is compiled either as module or into
	the kernel. See description for nls=name.

	uid=
	gid=
	umask= Provide default owner, group, and access mode mask.
	These options work as documented in mount(8). By
	default, the files/directories are owned by root and
	he/she has read and write permissions, as well as
	browse permission for directories. No one else has any
	access permissions. I.e. the mode on all files is by
	default rw------- and for directories rwx------, a
	consequence of the default fmask=0177 and dmask=0077.
	Using a umask of zero will grant all permissions to
	everyone, i.e. all files and directories will have mode
	rwxrwxrwx.

	fmask=
	dmask= Instead of specifying umask which applies both to
	files and directories, fmask applies only to files and
	dmask only to directories.

	sloppy=<BOOL> If sloppy is specified, ignore unknown mount options.
	Otherwise the default behaviour is to abort mount if
	any unknown options are found.

	show_sys_files=<BOOL> If show_sys_files is specified, show the system files
	in directory listings. Otherwise the default behaviour
	is to hide the system files.
	Note that even when show_sys_files is specified, "$MFT"
	will not be visible due to bugs/mis-features in glibc.
	Further, note that irrespective of show_sys_files, all
	files are accessible by name, i.e. you can always do
	"ls -l \$UpCase" for example to specifically show the
	system file containing the Unicode upcase table.

	case_sensitive=<BOOL> If case_sensitive is specified, treat all file names as
	case sensitive and create file names in the POSIX
	namespace. Otherwise the default behaviour is to treat
	file names as case insensitive and to create file names
	in the WIN32/LONG name space. Note, the Linux NTFS
	driver will never create short file names and will
	remove them on rename/delete of the corresponding long
	file name.
	Note that files remain accessible via their short file
	name, if it exists. If case_sensitive, you will need
	to provide the correct case of the short file name.

	disable_sparse=<BOOL> If disable_sparse is specified, creation of sparse
	regions, i.e. holes, inside files is disabled for the
	volume (for the duration of this mount only). By
	default, creation of sparse regions is enabled, which
	is consistent with the behaviour of traditional Unix
	filesystems.

	errors=opt What to do when critical filesystem errors are found.
	Following values can be used for "opt":
	continue: DEFAULT, try to clean-up as much as
	possible, e.g. marking a corrupt inode as
	bad so it is no longer accessed, and then
	continue.
	recover: At present only supported is recovery of
	the boot sector from the backup copy.
	If read-only mount, the recovery is done
	in memory only and not written to disk.
	Note that the options are additive, i.e. specifying:
	errors=continue,errors=recover
	means the driver will attempt to recover and if that
	fails it will clean-up as much as possible and
	continue.

	mft_zone_multiplier= Set the MFT zone multiplier for the volume (this
	setting is not persistent across mounts and can be
	changed from mount to mount but cannot be changed on
	remount). Values of 1 to 4 are allowed, 1 being the
	default. The MFT zone multiplier determines how much
	space is reserved for the MFT on the volume. If all
	other space is used up, then the MFT zone will be
	shrunk dynamically, so this has no impact on the
	amount of free space. However, it can have an impact
	on performance by affecting fragmentation of the MFT.
	In general use the default. If you have a lot of small
	files then use a higher value. The values have the
	following meaning:
	Value MFT zone size (% of volume size)
	1 12.5%
	2 25%
	3 37.5%
	4 50%
	Note this option is irrelevant for read-only mounts.


	Known bugs and (mis-)features
	=============================

	- The link count on each directory inode entry is set to 1, due to Linux not
	supporting directory hard links. This may well confuse some user space
	applications, since the directory names will have the same inode numbers.
	This also speeds up ntfs_read_inode() immensely. And we haven't found any
	problems with this approach so far. If you find a problem with this, please
	let us know.


	Please send bug reports/comments/feedback/abuse to the Linux-NTFS development
	list at sourceforge: linux-ntfs-dev@lists.sourceforge.net


	Using NTFS volume and stripe sets
	=================================

	For support of volume and stripe sets, you can either use the kernel's
	Device-Mapper driver or the kernel's Software RAID / MD driver. The former is
	the recommended one to use for linear raid. But the latter is required for
	raid level 5. For striping and mirroring, either driver should work fine.


	The Device-Mapper driver
	------------------------

	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://www.linux-ntfs.org/
	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 multiple 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 linux-ntfs-dev@lists.sourceforge.net 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.