Microsoft’s New File System ReFS

Let’s be frank NTFS (New Technology File System), which has been around since Windows NT (1993) definitely is overdue for either a makeover or a successor. Microsoft chose the latter deciding that the time for change has come and announced that the successor to NTFS, ReFS (Resilient File System) will roll out in it’s Windows Server 8 product. Though they’re rolling out a new file system the plan is to keep ReFS highly compatible with NTFS systems according to Surendra Verma, a development manager on the Windows Storage and File System team. One of the goals with ReFS, is to “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,” stated Verma.

ReFS will initially be introduced as a part of Windows Server 8 which is a path they’ve taken in the past with prior file systems (NTFS), with the desktop version of Windows 8 sticking to NTFS and future releases receiving support for ReFS. So what will ReFS offer or change for us? Plenty. ReFS will offer greater data integrity with checksums testing metadata (records that hold specifics to each file), the introduction of Integrity Streams, Large volume, file and directory sizes (eliminating the limitations of NTFS), Data Stripping and Shared storage pools across machines for additional fault tolerance.

Integrity streams which was mentioned above is an optional feature where the contents of each file is check-summed (redundancy check used to determine if there are errors). To help keep integrity and build resiliency to corruption, new writes (saves, edits, changes) are saved on a new location of the disk leaving the pre-existing data untouched (no overwrite) always leaving you with a verified working version if ever something happened such as a power failure or sudden system/program crash. Data stripping and shared storage pools allows for automatic corruption repair by telling Storage Spaces (expandable storage)  to read all of its copies of the data, select a good version based on its checksum, and use it to fix the corrupted copies.

Popular features such as BitLocker encryption, access-control lists (ACL’s) for security, mount points, volume snapshots and file IDs find there way in ReFS but not all of NTFS’ features were as fortunate. As Verma stated, in order to combat complexity and shrink the file systems footprint some features such as compression, file level encryption (EFS), user data transactions, extended attributes, and quotas would be dropped. While there is still much to learn about ReFS, due to the announcing and released blog post explaining and detailing the new file system, many questions have been raised.

Without quotas will there be another method for warning and enforcing limitations to keep users from filling up drive space? The same can be asked about compression. On drives/volumes where BitLocker can’t be used and with the dropped support for File level encryption (EFS) are we just SOL or forced to look to 3rd party support? While for the average user these questions’ and their answers matter not, the same cannot be said for system administrators and those who’d manage filer servers. Until such omissions are ironed out I find it hard to see ReFS as a full-time replacement for NTFS and in that regard I see NTFS sticking around for a bit. The appeal is there though with the highlighted emphasis on data integrity and new features such as Storage Spaces allowing users to configure storage for an entire machine, spanning multiple physical drives along with the data (and checksum metadata). The end result, ReFS should be a more flexible, reliable and scalable file system and experience for all even with some of the NTFS features being dropped.

Source: MSDN Blog