90. NTFS Single Instance Storage

• Abbreviated as SIS

• If several directories contain same exact file, only one instance will really exist.

• Two-part function:

  1. NTFS "filter" that manages the copies

  2. User space service Groveler searches for identical files to merge

• Again, this feature is designed for servers containing multiple installation programs in which many of the files could be the same coming from different distributions of software install packages.

• If SIS is disabled after it has been running, only the Groveler is disabled.

• The SIS file system "filter" component must remain active as long as there are merged files on the volume.

• There will be a SIS Common Store folder that contains information about which files are linked. If this folder is deleted, all of the linked files will become inaccessible.

• Reference:
  http://support.microsoft.com/default.aspx?scid=kb;en-us;299726