Single Instance Store
Single Instance Store (SIS) allows multiple images on the same RIS server to consume less disk space by combining duplicate files. This is the case for any type of operating system image files whether they are CD-based or RIPrep files on the RIS volume. This is especially useful when you store multiple RIPrep images on a RIS server. Usually, only 10 percent of the files (excluding installed applications) are different from the installed standard CD-based image. This saves a significant amount of disk space.
RISetup installs the two pieces that make up SIS: the SIS filter driver and the SIS Groveler. SIS is not necessary for RIS to work properly, and SIS can work independently of RIS. SIS can operate on any local volume except boot and system partitions.
The SIS filter driver is not removed when the rest of Remote Installation Services is removed. There might be files on the system that have been converted to SIS reparse points, and removing the driver causes those files to be inaccessible.