File Systems and File System Filter Drivers
Updated: August 25, 2012
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.
Filter Plugfest
The Filter Plugfest is an event for file system filter driver ISVs organized by the Microsoft File System Filters team. At this event, developers work with the ISVs to solve interoperability issues among various vendor solutions and the Filter Manager. There are also informative sessions on filter driver related issues, including the roadmap. Please check Filter Plugfest for upcoming Plugfests.
File System Filter Driver WDK ResourcesGetting started information, design guides, and reference topics are found in the Installable File Systems section in the Window Driver Kit (WDK) documentation. Design information for filter drivers is found in the File System Minifilter Drivers section. Studying samples is a practical way to see how File Systems and File System Filter Drivers are developed. Sample minifilter drivers are available in the MSDN Code Gallery. | File System Filter Driver CertificationCertification information for File Systems and File System Filter Drivers is found in the Windows Hardware Certification Kit (HCK). Tests for File Systems and File System Filter Drivers are found in the Filter.Driver category of the HCK. |
In addition to the WDK documentation, many other resources are available to assist in developing File Systems and File System Filter Drivers. Whitepapers, conference sessions, and standards specifications provide in-depth information on specific filter driver topics.
Filter Manager and Minifilters | File System Filter Driver Developer ResourcesHow to request allocation of an altitude from Microsoft. Subscribe to the NTFSD newsgroup for details about developing file systems and filter drivers. Obtain an ID for a filter driver that uses reparse points. OSR's "Developing File Systems for Windows" seminar explores developing file systems and File Systems and File System Filter Drivers. |
File System Filter Driver Topic Presentations |
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