A Description of the Functions of the Single Instance Storage Filter and the Groveler Service

This article describes the functions of the Groveler service and the Single Instance Storage Filter, what practices to avoid, and the recommended backup and restore procedures for the data that resides on a Single Instance Store (SIS) volume.

The Groveler Service

The Groveler service scans the hard-disk volumes on a Remote Installation Services (RIS) server for duplicate copies of files. If the service locates duplicate copies of files, one instance of the duplicate file is stored in a central folder, and the duplicates are replaced with a link (a reparse point) to the central copy to improve disk usage. If you stop this service, the files cannot be automatically linked, but the existing linked files can still be accessible.

NOTE: If you remove RIS from a Windows 2000-based computer, only the Groveler service is removed or disabled. When the Groveler service is either removed or disabled, it can prevent any future files that are copied to the volume from being copied to the SIS Common Store database folder and it can prevent the creation of a link (reparse point) to that data in the SIS database. By default, Windows 2000 does not remove or disable the Single Instance Storage Filter that can enable you to access the data in the SIS volume when RIS is removed.

The Single Instance Storage Filter

The Single Instance Storage Filter is a file system filter that manages the duplicate copies of files on hard-disk volumes. This filter copies one instance of the duplicate file into a central folder, and the duplicates are replaced with a link to the central copy to improve disk usage. This service (Single Instance Storage Filter) cannot be stopped. If this service is disabled, the linked files are not accessible. If the central folder is deleted, the linked files can become permanently inaccessible.

The Backup and Restore Procedures of Data Stored on a SIS Volume

It is recommended that you perform regular backups of critical data before you make any system changes or you install any services, especially those services that can interact with data.

To be able to access data that is stored on a SIS volume, you must either run or have installed Single Instance Storage Filter on your computer. The Single Instance Storage Filter driver is not installed by default on a new installation of Windows 2000 Server. This driver is only installed when the RIS is installed by means of the Add/Remove Programs tool (click Windows Components).

Additional Requirements

• The SIS volume, SIS Common Store folder, and reparse points (links) to the files must be restored to a Windows 2000 NTFS version 5.0 file system or partition that supports reparse points or junction points.
• The Single Instance Storage Filter must be installed or enabled to access the data in the SIS volume.
• The backup program must be capable and configured to backup and restore the reparse points or junction points (links) to the files, and the SIS volume and the SIS Common Store folder must be selected.

Recommended vs Not Recommended Practices

• CAUTION: You can lose data if you delete the SIS Common Store folder.
  
  It is not recommended to delete the SIS Common Store folder as all data that resides on the SIS volume can be lost. To save space, the actual files are copied (as previously mentioned) into the SIS Common Store database and only a link (reparse point) remains on the SIS volume. When you access this link, you are redirected to the actual data in the database.
• Typically, it is recommended (as an alternative) that you store unrelated RIS data on a volume other than the one that contains the RemoteInstall folder.
• It is not recommended to disable the Single Instance Storage Filter driver as the ability to access the data that is stored in the SIS volume (the SIS Common Store database) can be disabled. If you did disable the driver and you have data on the SIS volume that you need access to, you can enable the Single Instance Storage Filter with a startup type of "0x2" to re-establish access to the SIS volume. Refer to the previously mentioned article for more information.