Enhanced Write Filter
component of Windows XP Embedded and Windows Embedded Standard 7
Enhanced Write Filter (or EWF) is a component of Windows XP Embedded and Windows Embedded Standard 7 which stores volume changes on another medium instead of applying them to the original volume. Later it was renamed to Unified Write Filter (or UWF). EWF allows the writes to be discarded or committed to the original volume later (either directly or through inaction based on the configuration). As this minimizes writes to a specified hard disk, EWF and FBWF (File-Based Write Filter) have become popular in enthusiast computing as a way of decreasing wear of solid-state drives on netbooks and CarPCs.
Operating modes
EWF has three main operating modes: EWF Disk, EWF RAM, and EWF RAM Reg. In each mode, the location of the EWF volume (which stores the configuration) and the overlay volume (which stores file changes) is different. EWF Disk stores the overlay data outside the primary disk, allowing an external disk such as a CompactFlash to be used as an overlay. The EWF volume is stored in an unpartitioned space on the disk. EWF RAM stores the overlay data in the RAM and the EWF volume in an unpartitioned space on the disk. EWF RAM Reg is same as EWF RAM except the EWF volume is stored in Windows Registry.
The public source identifies “Enhanced Write Filter” as component of Windows XP Embedded and Windows Embedded Standard 7. This brief keeps that definition visible, then builds a research path around Enhanced, Write and Filter.
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This entry incorporates text from “Enhanced Write Filter” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.