Monday, May 28, 2012

pNFS in NetApp


In my last post I discussed about pNFS features and architecture, and promised that in next post I will discuss about NetApp’s implementation of pNFS. So here it is.

Since 1992, the time when NetApp was formed it is always known for its solid NFS implementation and frontrunner of NFS design and standardization. Today when NetApp has gone unified, and support not only NFS but SMB, FC, iSCSI, FCOE and some other less known protocols also, still it is a major driving force to NFS design. The latest example is pNFS where NetApp has proved again by delivering pNFS to its ONTAP 8.1 Cluster Mode offering.

In my opinion they have done a wonderful job with their implementation of pNFS, though currently it’s limited to support of file only, but heck yeah it’s wonderful. In NetApp’s implementation of pNFS not only data is distributed across all the nodes but metadata also. So if you have got metadata intensive workload you can tackle that as well by using round robin from your DNS infrastructure and instantly you have a cluster which not only scales linearly with data nodes but metadata nodes also.

Another niche feature is live volume transition. It gives flexibility to move a live volume in any node of cluster if ever required, that too non-disruptively. Thanks to pNFS, it keeps same NFS handle while data being served from new node so you don’t need to unmounts and remount the filesystem and since we use cluster wide namespace no change is required at its directory location also. Isn’t this sweet, no more struggling to get downtime to move a volume, huh!

And the best part is that it’s built around industry standard set by IETF, so there is no requirement of special client software and you can use it along with NFS version 3, 4 or 4.1 without pNFS supported client.

The only setback from using it across your environment is limited client support. As of today, only Fedora 16 with kernel 2.6.39 and RHEL 6.2 can be used, however soon we will see its support in other distributions also as it’s already in kernel mainstream and it will not be long when other distributions start shipping it.

References:
http://media.netapp.com/documents/wp-7153.pdf
http://media.netapp.com/documents/tr-4063.pdf
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