File Systems and File System Filter Drivers

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The file systems in Windows are implemented as file system drivers working above the storage system. Each of the file systems in Windows are designed to provide reliable data storage with varying features to meet the user’s requirements. A comparison of features for each of the standard file systems in Windows is found here. New in Windows 8 is ReFS. ReFS is a file system with scalable large volume support and the ability detect and correct data corruption on disk.

Creating a new file system driver in addition to those supplied in Windows is likely unnecessary. File Systems and File System Filter Drivers can provide any customized behavior required to modify the operation of existing file systems.
File System Filter Driver Development

A file system filter driver intercepts requests targeted at a file system or another file system filter driver. By intercepting the request before it reaches its intended target, the filter driver can extend or replace functionality provided by the original target of the request. Examples of File Systems and File System Filter Drivers include anti-virus filters, backup agents, and encryption products.

File system filtering services are available through the Filter Manager in Windows. The Filter Manager provides a framework for developing File Systems and File System Filter Drivers without having to manage all the complexities of file I/O. The Filter Manager simplifies the development of third-party filter drivers and solves many of the problems with the existing legacy filter driver model, such as the ability to control load order through an assigned altitude. A filter driver developed to the Filter Manager model is called a minifilter. Every minifilter driver has an assigned altitude, which is a unique identifier that determines where the minifilter is loaded relative to other minifilters in the I/O stack. Altitudes are allocated and managed by Microsoft.