Microsoft introduced the Resilient File System, or ReFS, with Windows Server 2012. Codenamed “Protogon,” it was designed as a modern successor-oriented file system for large, resilient storage rather than as an immediate universal replacement for NTFS.
ReFS emphasizes protection against corruption, scalability, and integration with Storage Spaces. It uses checksums and metadata structures based on B+ trees, and supported configurations can detect damaged data and recover from mirrored copies. Its design was particularly relevant to file servers and virtualization workloads, where storage capacity and fault tolerance are important.
The first release did not support every NTFS feature. For example, early ReFS versions lacked capabilities such as file compression, Encrypting File System support, hard links, and booting Windows from a ReFS volume. Some functionality expanded in later Windows and Windows Server releases, so descriptions of ReFS can differ depending on the version being discussed.
ReFS is commonly confused with FAT32 or exFAT because all are file systems, but they serve different roles. FAT32 and exFAT prioritize broad compatibility with removable media, while ReFS is primarily associated with Windows server and specialized storage scenarios.