Enhanced Write Filter (or EWF) is a component of

Windows XP Embedded Windows XP, which is the next version of Windows NT after Windows 2000 and the successor to the consumer-oriented Windows Me, has been released in several editions since its original release in 2001. Windows XP is available in many languages. In ...

and

Windows Embedded Standard 7 Windows IoT, formerly Windows Embedded, is a family of operating systems from Microsoft designed for use in embedded systems. Microsoft currently has three different subfamilies of operating systems for embedded devices targeting a wide market, ...

which stores

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...

changes on another medium instead of applying them to the original volume. 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 Enthusiast computing refers to a group of people who build high-end personal computers that facilitate gaming, stock trading, video editing, music creation and editing, photograph editing, programming, remote work, cryptocurrency mining, and o ...

as a way of decreasing wear of

solid-state drive A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is a ...

s 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 CompactFlash (CF) is a flash memory mass storage device used mainly in portable electronic devices. The format was specified and the devices were first manufactured by SanDisk in 1994. CompactFlash became one of the most successful of the e ...

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

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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 Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and ...

Use in Windows Vista

As is the case with the appropriation of EWF in CarPCs, which are more often based on Windows XP because of its smaller "footprint," it has been used with similar effect in Windows Vista NetBooks to diminish write activity to, and so enhance the lifespan of solid-state drives (SSD). Due to changes in Windows Vista, however, the Disk Mode can not be used.

Potential pitfalls

Unlike most commercial

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s, EWF cannot reclaim the RAM after files have been deleted from it. In EWF RAM (and EWF RAM Reg) mode, the memory consumed only ever increases. Eventually the system will have no more free space and will crash. Automatic adjustment of daylight saving time is not compatible with EWF, causing incorrect time settings at each reboot.Write Filters and Automatic Adjustment of Daylight Saving Time (Standard 7 SP1)
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References

{{Microsoft Windows components Windows XP Windows components