ReFS: The next generation file system (Part 2)

In my previous blog post we discussed the introduction of a brand new file system in Windows Server 2012 (and Windows 8) called ReFS (Resilient File System). You can find the previous post here. ReFS is built on the premise that to have access to data reliably you don’t have to rely on expensive storage solution. ReFS provides the layer of robustness by ensuring the integrity, availability and scalability of data that expensive storage solutions cannot provide in a cost effective manner. Since ReFS has the context of the data being written to the underlying storage, it can perform proactive error checking and correction that underlying storage cannot detect and correct. All in all, ReFS is a much needed file system where NTFS (New Technology File System) has dominated the Windows world for more than a decade (nearly two decades). But NTFS inherently lacked the robustness required to protect data from events like power failures and also have the ability to perform consistency and integrity checks without taking the file system offline. But there are limitations to ReFS too and this blog post sheds some light on those.

1. ReFS cannot be configured on the boot drives. The boot drives have to be configured with NTFS.
2. There does not seem to be anyway to convert a NTFS file system to ReFS.  This is especially important if an existing disk configured with NTFS is attached to a Windows 8 or Windows Server 2012 system and you want to leverage the new robust file system features of ReFS.
3. ReFS cannot be used on removable media.  Given that removable media can undergo more wear and tear, having a file system like ReFS, where integrity and consistency is the focus, would have been helpful.
4. Deduplication is not supported on volumes formatted with ReFS. This is also a huge limitation. One of the more common use cases of ReFS will be as the data storage for file servers. With the introduction of deduplication in Windows Server 2012 and Windows 8, data stored on file servers would have greatly benefited by this feature. But now one has to choose between resiliency and storage optimization. A choice many administrators would not be happy about.
5. While ReFS maintains a great deal of backward compatibility with NTFS there are many features of NTFS that are no longer supported (deprecated):
   1. 8.3 short names (DOS remnants) – the ability to access a file in the DOS format of 8 characters for the name followed by a dot followed by 3 characters for the extension.
   2. Compressed files – the ability for the file system to compress data
   3. Encrypted files – the ability for the file system to encrypt data
   4. Extended attributes – the ability for the files to have additional metadata stored with the file data.
   5. Named streams – the ability to have multiple data streams within a file, with distinct names for each data stream
   6. Sparse files – the ability to create a file of a certain size without physically allocating the space for it on disk up at file creation.
   7. Hard links – the ability to have alias for a given file.

I am sure there will be incremental improvement to ReFs in the forthcoming service packs and Windows versions. ReFS gives Windows the vehicle to expand into the cloud at a low backing storage cost and still have all the robustness that is required in a high I/O environment. Have you configured and played with Windows Server 2012? Let us know your experience; we’d love to hear about it.