Features NTFS reparse point

1 features

1.1 volume mount points
1.2 directory junctions
1.3 symbolic links
1.4 distributed link tracking (dlt)
1.5 single instance storage (sis)
1.6 hierarchical storage management (hsm)
1.7 native structured storage (nss)

features
volume mount points

volume mount points similar unix mount points, root of file system attached directory. in ntfs, allows additional file systems mounted without requiring separate drive letter (such c: or d:) each.

once volume has been mounted on top of existing directory of volume, contents listed in directory become invisible , replaced content of root directory of mounted volume. mounted volume still have own drive letter assigned separately. file system not allow volumes mutually mounted on each other. volume mount points can made either persistent (remounted automatically after system reboot) or not persistent (must manually remounted after reboot).

mounted volumes may use other file systems ntfs, possibly own security settings , remapping of access rights according remote file system policy.

directory junctions

directory junctions similar volume mount points, reference other directories in file system instead of other volumes. instance, directory c:\exampledir directory junction attribute contains link d:\linkeddir automatically refer directory d:\linkeddir when accessed user-mode application. function conceptually similar symbolic links directories in unix, except target in ntfs must directory (typical unix file systems allow target of symbolic link type of file).

directory junctions (which can created command mklink /j junctionname targetdirectory , removed rmdir junctionname console prompt) persistent, , resolved on server side share same security realm of local system or domain on parent volume mounted , same security settings contents content of target directory; junction may have distinct security settings. unlinking directory junction not delete files in target directory.

some directory junctions installed default on windows vista, compatibility previous versions of windows, such documents , settings in root directory of system drive, links users physical directory in root directory of same volume. hidden default, , security settings set windows explorer refuse open them within shell or in applications, except local built-in system user or local administrators group (both user accounts used system software installers). additional security restriction has been made avoid users of finding apparent duplicate files in joined directories , deleting them error, because semantics of directory junctions not same hardlinks; reference counting not used on target contents , not on referenced container itself.

directory junctions soft links (they persist if target directory removed), working limited form of symbolic links (with additional restriction on location of target), optimized version allowing faster processing of reparse point implemented, less overhead newer ntfs symbolic links, , can resolved on server side (when found in remote shared directories).

symbolic links

symbolic links (or soft links) introduced in windows vista. symbolic links resolved on client side. when symbolic link shared, target subject access restrictions on client, , not server.

symbolic links can created either files (created mklink symlink targetfilename) or directories (created mklink /d symlinkd targetdirectory), (unlike unix symbolic links) semantic of link must provided created link. target need not exist or available when symbolic link created: when symbolic link accessed , target checked availability, ntfs check if has correct type (file or directory); return not-found error if existing target has wrong type.

they can reference shared directories on remote hosts or files , subdirectories within shared directories: target not mounted @ boot, temporarily on demand while opening them openfile() or createfile() api. definition persistent on ntfs volume created (all types of symbolic links can removed if files, using del symlink command line prompt or batch).

distributed link tracking (dlt)

distributed link tracking allows applications track files, shell shortcuts or ole links if renamed or moved volume within same machine, domain or workgroup. tracking implemented system service, uses object identifier (oid) index stored in metafile. when application requests track file or directory, tracking service creates oid entry, points file, , file rename, copy or move operation ntfs v3 volume copies object id. allows tracking service find target file.

single instance storage (sis)

when there several directories have different similar files, of these files may have identical content. single instance storage allows identical files merged 1 file , create references merged file. sis consists of file system filter manages copies, modification , merges files; , user space service (or groveler) searches files identical , need merging. sis designed remote installation servers these may have multiple installation images contain many identical files; sis allows these consolidated but, unlike example hard links, each file remains distinct; changes 1 copy of file leave others unaltered. similar copy-on-write, technique memory copying not done until 1 copy modified.

hierarchical storage management (hsm)

hierarchical storage management means of transferring files not used period of time less expensive storage media. when file next accessed, reparse point on file determines needed , retrieves storage.

native structured storage (nss)

nss activex document storage technology has since been discontinued microsoft. allowed activex documents stored in same multi-stream format activex uses internally. nss file system filter loaded , used process multiple streams transparently application, , when file transferred non-ntfs formatted disk volume transfer multiple streams single stream.