The new file system introduced in the latest windows 8 Resilient File System, or ReFS, as a "next generation file system" built on the foundations of the NTFS. By reusing NTFS' API / semantics engine, ReFS hopes to retain a high level of compatibility with NTFS features. Underneath the existing semantics engine, the new file system introduces a new storage engine that hopes to protect against latent disk errors, resist data corruption, uphold metadata integrity, grant large volume, file and directory size -- and well, just build a better storage system in general.
* Maintain a high degree of compatibility with a subset of NTFS features that are widely adopted while deprecating others that provide limited value at the cost of system complexity and footprint.
* Verify and auto-correct data. Data can get corrupted due to a number of reasons and therefore must be verified and, when possible, corrected automatically. Metadata must not be written in place to avoid the possibility of “torn writes,” which we will talk about in more detail below.
* Optimize for extreme scale. Use scalable structures for everything. Don’t assume that disk-checking algorithms, in particular, can scale to the size of the entire file system.
* Never take the file system offline. Assume that in the event of corruptions, it is advantageous to isolate the fault while allowing access to the rest of the volume. This is done while salvaging the maximum amount of data possible, all done live.
* Provide a full end-to-end resiliency architecture when used in conjunction with the Storage Spaces feature, which was co-designed and built in conjunction with ReFS.
The key features of ReFS are as follows (note that some of these features are provided in conjunction with Storage Spaces).
* Metadata integrity with checksums
* Integrity streams providing optional user data integrity
* Allocate on write transactional model for robust disk updates (also known as copy on write)
* Large volume, file and directory sizes
* Storage pooling and virtualization makes file system creation and management easy
* Data striping for performance (bandwidth can be managed) and redundancy for fault tolerance
* Disk scrubbing for protection against latent disk errors
* Resiliency to corruptions with "salvage" for maximum volume availability in all cases
* Shared storage pools across machines for additional failure tolerance and load balancing
In addition, ReFS inherits the features and semantics from NTFS including BitLocker encryption, access-control lists for security, USN journal, change notifications, symbolic links, junction points, mount points, reparse points, volume snapshots, file IDs, and oplocks.
And of course, data stored on ReFS is accessible through the same file access APIs on clients that are used on any operating system that can access today’s NTFS volumes.
FAQ:
Q) Why is it named ReFS?
ReFS stands for Resilient File System. Although it is designed to be better in many dimensions, resiliency stands out as one of its most prominent features.
Q) What are the capacity limits of ReFS?
The table above shows the capacity limits of the on-disk format. Other concerns may determine some practical limits, such as the system configuration (for example, the amount of memory), limits set by various system components, as well as time taken to populate data sets, backup times, etc.
Q) Can I convert data between NTFS and ReFS?
In Windows 8 there is no way to convert data in place. Data can be copied. This was an intentional design decision given the size of data sets that we see today and how impractical it would be to do this conversion in place, in addition to the likely change in architected approach before and after conversion.
Q) Can I boot from ReFS in Windows Server 8?
No, this is not implemented or supported.
Q) Can ReFS be used on removable media or drives?
No, this is not implemented or supported.
Q) What semantics or features of NTFS are no longer supported on ReFS?
The NTFS features we have chosen to not support in ReFS are: named streams, object IDs, short names, compression, file level encryption (EFS), user data transactions, sparse, hard-links, extended attributes, and quotas.
Q) What about parity spaces and ReFS?
ReFS is supported on the fault resiliency options provided by Storage Spaces. In Windows Server 8, automatic data correction is implemented for mirrored spaces only.
Q) Is clustering supported?
Failover clustering is supported, whereby individual volumes can failover across machines. In addition, shared storage pools in a cluster are supported.
Q) What about RAID? How do I use ReFS capabilities of striping, mirroring, or other forms of RAID? Does ReFS deliver the read performance needed for video, for example?
ReFS leverages the data redundancy capabilities of Storage Spaces, which include striped mirrors and parity. The read performance of ReFS is expected to be similar to that of NTFS, with which it shares a lot of the relevant code. It will be great at streaming data.
Q) How come ReFS does not have deduplication, second level caching between DRAM & storage, and writable snapshots?
ReFS does not itself offer deduplication. One side effect of its familiar, pluggable, file system architecture is that other deduplication products will be able to plug into ReFS the same way they do with NTFS.
ReFS does not explicitly implement a second-level cache, but customers can use third-party solutions for this.
ReFS and VSS work together to provide snapshots in a manner consistent with NTFS in Windows environments. For now, they don’t support writable snapshots or snapshots larger than 64TB.
Source :- Building of windows8
