Microsoft engineers file system for the Windows 8 era

Microsoft's new file system, ReFS, can host filenames as long as 32,000 characters

The upcoming release of Windows Server 8 will feature an entirely new file system, called ReFS, that addresses many of the shortcomings of the aging NTFS (New Technology File System) now used across all current Windows editions, the company announced Tuesday in a blog.

Over time, Microsoft expects to use the file system to replace NTFS for the desktop and other versions of Windows as well, noted Microsoft Windows President Steven Sinofsky, in a preface to the blog post.

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The file system is being designed to work for a wide range of devices "from the smallest footprint machines to the largest data centers," said Microsoft development manager Surendra Verma in the blog post. ReFS will be able to support file names and file paths with as many as 32,000 characters. It can host files as large as 18 quintillion bytes, and host as many as 18 quintillion files.

ReFS (Resilient File System) will maintain backward compatibility, for the most part, with NTFS, but adds new features to support the wider array of uses. For instance, the new file system won't require mandatory periodic checkdisk operations, which can slow the booting of very large disks. It can also be repaired without taking the entire system offline, which could be handy for mission-critical duties. The new file system can autocorrect data that has been written incorrectly to disk.

"What I see Microsoft here is taking much of what we have learned about how filesystems are used and pushing that further into the stack," said IDC analyst Al Hilwa. "The overall focus appears to be uptime and recoverability. In principle these techniques are already in use by storage vendors, but integrating into the file system makes it possible to offer even more resilient services to users and enterprises down the road."

Some NTFS features will be deprecated, notably those that are little used or add undue complexity. NTFS's Object IDs, short names, compression, file level encryption, hard-links, extended attributes, and quotas won't be supported in ReFS. Other aspects of NTFS, such as BitLocker encryption, access control, symbolic links, mount points, volume snapshots and file IDs, will be preserved. And client APIs (application programming interfaces) written for NTFS won't need to be changed when they start communicating with ReFS-based systems, the company promised.

The new file system will first be available in the release of Windows Server 8. At first it will be used only for server storage, and, at some point after this release, it will be upgraded to use for client data storage and then, finally, be used as the operating system's primary boot volume. Microsoft offered no indication when ReFS will be harnessed for other versions of Windows 8. "So the impact on end users is limited in the early days," Hilwa said.

Joab Jackson covers enterprise software and general technology breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is

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