What type of file system is ReFS?

ReFS, which stands for Resilient File System, is designed primarily for data integrity and is intended for use with large-scale data storage and enterprise scenarios. Although it was introduced by Microsoft and represents an advancement in file system technology, it is not as widely adopted as NTFS, which is the traditional file system for Windows. ReFS is still evolving, with ongoing updates and features being added. It is specifically tailored for scenarios that require high availability and fault tolerance, such as data centers and virtualization infrastructure.

The option stating that ReFS is a file system still in development reflects its niche positioning and the fact that it is not as prevalent or universally applicable compared to more established file systems. While it has been released and is functional within specific use cases, it is not yet the go-to file system for general consumer use. Thus, its development status and targeted applications align with this option's characterization of ReFS.

ReFS’s proprietary nature is restricted to Microsoft platforms, but it is not used exclusively by Apple, nor is it a standard format for all operating systems, which would exclude many other file systems used in different environments.