Volume Shadow Copy (VSS)
Efficiently keeps historical versions of files and folders on NTFS volumes by copying old, newly-overwritten data to shadow copy (copy-on-write). The old file data is overlaid on the new when the user requests a revert to an earlier version. On heavily loaded systems, Microsoft recommends setting up a shadow copy volume on separate disk to reduce the I/O load on the main volume.
File compression
NTFS can compress files using a variant of the LZ77 algorithm (also used in the popular ZIP file format). [6] Although read-write access to compressed files is transparent, Microsoft recommends avoiding compression on server systems and/or network shares holding roaming profiles because it puts a considerable load on the processor. Single-user systems with limited hard disk space will probably use NTFS compression successfully. The slowest link in the 2.5 inch drive of a notebook computer is not the CPU, but the speed of the drive, so NTFS compression allows the limited storage spce to be better used.
Single Instance Storage (SIS)
When there are several directories that have different, but similar files, some of these files may have identical content. Single instance storage allows identical files to be merged to one file and create references to that merged file. SIS consists of a file system filter that manages copies, modification and merges to files; and a user space service (or groveler) that searches for files that are identical and need merging. SIS was mainly designed for remote installation servers as these may have multiple installation images that contain many identical files; SIS allows these to be consolidated but, unlike for example hard links, each file remains distinct; changes to one copy of a file will leave others unaltered.
Encrypting File System (EFS)
Provides strong and user-transparent encryption of any file or folder on an NTFS volume. EFS works in conjunction with the EFS service, Microsoft’s CryptoAPI and the EFS File System Run-Time Library (FSRTL). As of February 2004, its encryption has not been compromised.
EFS works by encrypting a file with a bulk symmetric key (also known as the File Encryption Key, or FEK), which is used because it takes a relatively smaller amount of time to encrypt and decrypt large amounts of data than if an asymmetric key cipher is used. The symmetric key that is used to encrypt the file is then encrypted with a public key that is associated with the user who encrypted the file, and this encrypted data is stored in an alternate data stream of the encrypted file. To decrypt the file, the file system uses the private key of the user to decrypt the symmetric key that is stored in the file header. It then uses the symmetric key to decrypt the file. Because this is done at the file system level, it is transparent to the user. [9] Also, in case of a user losing access to their key, support for recovery agents that can unencrypt files has been built in to the EFS system.
Symbolic links
Introduced in Windows Vista onward, they are similar to Windows’ shortcuts, but inside the NTFS’ metadata. The new NTFS symbolic links work in a similar way to the symbolic links that have existed in Linux and similar operating systems since the early days of Unix.
