Parallel NFS (pNFS) and Layouts
Parallel NFS (pNFS) represents a major step forward in the development of NFS. Ratified in January 2010 and described in RFC-5661, pNFS depends on the NFS client understanding how a clustered filesystem stripes and manages data. It's not an attribute of the data, but an arrangement between the server and the client, so data can still be accessed via non-pNFS and other file access protocols. pNFS benefits workloads with many small files, or very large files, especially those run on compute clusters requiring simultaneous, parallel access to data.
Some Proposed NFSv4.2 features
NFSv4.2 promises many features that end-users have been requesting, and that makes NFS more relevant as not only an "every day" protocol, but one that has application beyond the data center. As the requirements document for NFSv4.2 puts it, there are requirements for:- High efficiency and utilization of resources such as, capacity, network bandwidth, and processors.
- Solid state flash storage which promises faster throughput and lower latency than magnetic disk drives and lower cost than dynamic random access memory.
Server Side Copy
Server-Side Copy (SSC) removes one leg of a copy operation. Instead of reading entire files or even directories of files from one server through the client, and then writing them out to another, SSC permits the destination server to communicate directly to the source server without client involvement, and removes the limitations on server to client bandwidth and the possible congestion it may cause.Application Data Blocks (ADB)
ADB allows definition of the format of a file; for example, a VM image or a database. This feature will allow initialization of data stores; a single operation from the client can create a 300GB database or a VM image on the server.Guaranteed Space Reservation & Hole Punching
As storage demands continue to increase, various efficiency techniques can be employed to give the appearance of a large virtual pool of storage on a much smaller storage system. Thin provisioning, (where space appears available and reserved, but is not committed) is commonplace, but often problematic to manage in fast growing environments. The guaranteed space reservation feature in NFSv4.2 will ensure that, regardless of the thin provisioning policies, individual files will always have space available for their maximum extent.
Obtaining Servers and Clients
With this background on the features of NFS, there is considerable interest in the end-user community for NFSv4.1 support from both servers and clients. Many Network Attached Storage (NAS) vendors now support NFSv4, and in the last 12 months, there has been a flurry of activity and many developments in server support of NFSv4.1 and pNFS. For NFS server vendors, there are NFSv4.1 and files based, block based and object based implementations of pNFS available; refer to the vendor websites, where you will get the latest up-to-date information. On the client side, there is RedHat Enterprise Linux 6.4 that includes full support for NFSv4.1 and pNFS (see www.redhat.com), Novell SUSE Linux Enterprise Server 11 SP2 with NFSv4.1 and pNFS based on the 3.0 Linux kernel (see www.suse.com), and Fedora available at fedoraproject.org.Conclusion
NFSv4.1 includes features intended to enable its use in global wide area networks (WANs). These advantages include:- Firewall-friendly single port operations
- Advanced and aggressive cache management features
- Internationalization support
- Replication and migration facilities
- Optional cryptography quality security, with access control facilities that are compatible across UNIX ® and Windows ®
- Support for parallelism and data striping
- What is NFS: A Brief Introduction (Download webcast slides)
- NFS Mini-Series - Part 1 - Four Reasons to Start Working with NFSv4.1 Now (Download webcast slides)
- NFS Mini-Series - Part 2 - Advances in NFS, NFSv4.1, pNFS and NFSv4.2 (Download webcast slides)
- NFS Mini-Series - Part 3 - NFS: Plan for a Smooth Migration (Download webcast slides)
- NFS Mini-Series - Part 4 - Understanding and Implementing pNFS (Download webcast slides)
- What's New in NFSv4.2 (Download webcast slides)
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