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 which stores
volume
Volume is a measure of regions in 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) ...
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
A gaming computer, also known as a gaming PC, is a specialized personal computer designed for playing PC games at high standards. They typically differ from mainstream personal computers by using high-performance graphics cards, a high core-co ...
as a way of decreasing wear of
solid-state drive
A solid-state drive (SSD) is a type of solid-state storage device that uses integrated circuits to store data persistently. It is sometimes called semiconductor storage device, solid-state device, or solid-state disk.
SSDs rely on non- ...
s on
netbook
A netbook is a small-sized laptop computer; they were primarily sold from 2007 until around 2013, designed mostly as a means of accessing the Internet and being significantly less expensive than regular-sized laptops.
At their inception in l ...
s 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
RAM
Ram, ram, or RAM most commonly refers to:
* A male sheep
* Random-access memory, computer memory
* Ram Trucks, US, since 2009
** List of vehicles named Dodge Ram, trucks and vans
** Ram Pickup, produced by Ram Trucks
Ram, ram, or RAM may also ref ...
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, a ...
.
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
RAM disk
A RAM drive (also called a RAM disk) is a block of random-access memory ( primary storage or volatile memory) that a computer's software is treating as if the memory were a disk drive (secondary storage). RAM drives provide high-performance te ...
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)
/ref>
See also
* OverlayFS
References
{{Microsoft Windows components
Windows XP
Windows components