Unified Write Filter
A Unified Write Filter is a filter driver that seals the drive in a non-write view and then keeps a differencing area in RAM of all the changes the user makes during the session. This area is known as the UWF overlay. This is a virtual storage area that looks at all the intended writes for the protected storage area. Instead of performing the write, it reads that disk sector from disk, then modifies it as the write was supposed to, and holds that change and caches it in memory (unless a page-file is in use; then it can make use of the page-file to extend the overlay area).
This is the biggest drawback of UWF. Typically, embedded devices do not have a preponderance of RAM installed (they are supposed to be cheaper than ...
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