First off, WinFS was a technology designed as a relational file system for the storage of structured and unstructured data. After several years of hype, it was essentially quietly killed in 2006.
The main factors for its death laid around the fact that it didn't offer a significantly better experience than what we already had with NTFS.
So fast forwarding to today, with NTFS as the dominate file system (though many legacy devices still use FAT-32), what makes ReFS worth the change?
First off, Windows 8 is all about change with its touch-centric design, its use of the hibernate kernel for speeding up start-ups and shut-downs, and the introduction of ARM processor support. So now seems like the perfect time to make yet a big change on the file system front as well.
Microsoft is working hard to overcome past perceptions that its Oses are easily corrupted and overly unstable when compared to options like Linux and Mac OS. Despite that fact this has been somewhat true, the folks at Redmond still find it important to lay these security and stability concerns to rest.
So ReFS standards for “resilient” file system, and resilient it is. The main purpose that designers kept in mind with this format is that it is capable of keeping data safe and, hopefully, free of potential corruptibility.
There are several ways it attempts to accomplish this goal, such as keeping metadata integrity with checksums, verifying and auto-correcting data to limit data corruption, isolating data corruption, keeping user data integrity with integrity streams, and keeping an entire volume intact, online, and accessible.