File System Recognizers

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文件系统识别器（FSR）是一种轻量级的Windows内核模式设备驱动程序，用于识别物理媒介上的文件系统格式并加载相应的完整文件系统驱动程序（FSD）。通过检查磁盘上的签名来确定是否加载特定的文件系统，从而节省系统资源。

File System Recognizers

转自：http://dododododo.blog.sohu.com/

分类： Nt System 2006-06-22 11:36

File System Recognizers

First, a file system recognizer is a standard Windows NT kernel mode device driver which serves a single simple task—it looks at physical media devices and, if it recognizes the media format, it loads the full file system driver.

Why not just load the entire file system? Since the full file system driver might never be required on the system, using a little driver can save several hundred kilobytes of precious system memory. For example, on a system where the CD-ROM is never accessed, the CDFS file system need never be loaded—saving that memory for more important operations.

How does a file system recognizer determine that its file system is present on a disk? Typically, this is done by examining a signature on the disk. This signature might include information within the partition table, a unique value located at a particular byte offset from the beginning of the partition, and the serial number or whatever other clever mechanism the developer might have defined.

An FSR analyzes the media to determine if it contains a recognized file system. However, instead of mounting the drive, the FSR loads the FSD. Once the FSD is loaded, the FSR can unload since its task is done.When the File System Driver (FSD) is loaded, it is responsible for analyzing the disk and determining if the media contains a recognized file system. If it does, the FSD will then mount the drive.