Windows 8 (or rather Windows Server 2012) introduced a new file system called ReFS. ReFS stands for Resilient File System. Codenamed "Protogon", it improves on NTFS in some respects, while also removing a number of features. You may read about the advantages of ReFS in the following Wikipedia article. ReFS is intended for file servers only. In Windows 8.1, it is in fact locked for server OS only. If you need to unlock and enable full read and write support for ReFS in Windows 8.1, you can follow these simple instructions in this article.