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What are the implications of NFS 4.1 in vSphere 6?

VMware's vSphere 6 is one of the first major products to support NFS 4.1, but the benefits may not outweigh the risks to use this storage protocol.

The network file system (NFS) protocol allows client computers to access files across a network. In effect, NFS...

allows network storage access which looks and feels a lot like local storage access.

NFS 3 was ratified in June 1995 and it became one of the first NFS protocols widely adopted by an IT industry that was just beginning to recognize the importance of networks. Version 3 supported 64-bit file sizes, server-side write improvements and improved communicating file attributes along with file names. NFS 3 also used TCP as a transport layer, making it a fit with TCP-based networks like Ethernet and allowing NFS over WAN connections, such as the Internet.

But NFS 3 suffers from several noteworthy limitations. As a stateless protocol, it cannot lock or manage access to shared data. NFS 3 is also limited in scope -- a client system can only communicate with one server at one time -- and this can impair the potential of NFS in today's busy virtualized environments with heavy I/O traffic.

NFS 4 was developed to improve performance, add stateful operation to enhance data sharing, and add security features like support for Kerberos authentication. NFS 4 was first ratified in December 2000, updated to NFS 4.1 in January 2010, and revised again in March 2015. The move to NFS 4.1 added parallelism to the protocol, allowing a client system to access multiple content streams simultaneously. But even with 15 years of history, NFS 4.x has not been widely adopted. By comparison, protocols like SMB 3.0 released by Microsoft in 2012 have received far more attention. VMware's vSphere 6 is one of the first major vendors to adopt NFS 4.1.

But the move to NFS 4.1 isn't quite so simple. NFS 4.1 in vSphere 6 supports high availability, virtual machine migration and distributed resource scheduler (DRS), but doesn't yet support storage DRS, Virtual Volumes or site recovery manager. Even more disappointing, vSphere 6 doesn't support parallel NFS capabilities -- though there is multipathing -- and there is no compatibility between NFS 3 and NFS 4.1. These shortcomings will impair NFS performance and pose serious issues for migrations; you can't migrate an NFS 3 volume to an NFS 4.1 volume -- and vice versa. This means careful storage planning is needed to ensure migrations don't move between differing NFS versions.

Many administrators may choose to experiment with the new features NFS 4.1 supports, but hold off on broad NFS 4.1 deployment until more of vSphere's advanced features are supported.

This was last published in June 2015

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