The image store is a collection of image groups that stores the .wim images and helps the client computer obtain and install the images. An image group is a collection of images that share security options and file resources. An image group consists of the following two components:
- The Res.rwm file. The resource .wim
file (Res.rwm) contains the file resources for all of the images in
an image group. Each image group has its own Res.rwm file. File
resources are single-instanced because they are shared across the
image group. To service an image (for example, to apply an update),
you must have access to the Res.rwm file. Although the file name
seems to indicate otherwise, the .rwm file is actually a .wim
- <imagename>.wim files. Each .wim
image file contains the metadata that describes the image, but the
actual file resources for the image reside in Res.rwm.
The storage structure of the image group uses the imaging feature called “capture by reference.” This feature is most commonly used with “split” .wim files, which are the smaller pieces that result when you break up a large .wim file (typically so that you can fit the pieces of the file onto CDs). The image store in Windows Deployment Services takes this concept a step farther by creating a split media set consisting of two parts: one part that contains an “empty” .wim file that contains only the definition of the image, and another part that contains all the file resources for an image. This storage method is more efficient than the Single Instance Store service used in Remote Installation Services (RIS) in Windows Server 2003.