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ReFS || next generation file system for Windows


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. It will come with Windows 8.

Q) What are the capacity limits of ReFS?

The table below 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.

Attribute Limit based on the on-disk format
Maximum size of a single file 2^64-1 bytes
Maximum size of a single volume Format supports 2^78 bytes with 16KB cluster size (2^64 * 16 * 2^10). Windows stack addressing allows 2^64 bytes
Maximum number of files in a directory 2^64
Maximum number of directories in a volume 2^64
Maximum file name length 32K 255 unicode characters (for compatibility this was made consistent with NTFS for the RTM product)
Maximum path length 32K
Maximum size of any storage pool 4 PB
Maximum number of storage pools in a system No limit
Maximum number of spaces in a storage pool No limit


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.

Complete Post : http://blogs.msdn.com/b/b8/archive/2012/01/16/building-the-next-generation-file-system-for-windows-refs.aspx

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