ReFS (Resilient File System) is a file system designed for next-generation operating systems, such as Windows Server 8.  ReFS combats bit rot (the corruption of bits in a file system over time) through disk scrubbing tasks that read and validate data. It maintains a high level of compatibility with NTFS and builds on that foundation

to be more consistent and never result in downtime. However, ReFS is not supported on removable media and NTFS data can’t be converted. It does not natively offer deduplication, but third-party dedupe software will continue to work.

The Resilient File System relies on the previously existing NTFS code base, although it will not support previous features such as named streams, sparse files, and quotas. ReFS works with Storage Spaces, a system that creates a pool of hardware and virtual storage devices and ensures the protection of data on that system, similar to a RAID array. ReFS will be production-ready when Windows 8 ships, but it can only be used with Windows Server 8 as a storage space. This means a disk formatted with ReFS, in its current state, cannot act as a bootable drive.

Key features of ReFS include:
• Metadata integrity
• Integrity streams
• Copy on write
• Large volume, file and directory sizes
• Storage pooling and virtualization
• Data striping for performance (similar to RAID)
• Disk scrubbing
• Resiliency to corruption
• Compatible with shared storage pools