zlacker

>>chmayn+(OP)
Of course, the first commenter "willy" repeats the canard that statelessness makes no sense:

> The very notion of a stateless filesystem is ridiculous. Filesystems exist to store state.

It's the protocol that's stateless, not the filesystem. I thought the article made a reasonable attempt to explain that.

Overall the article is reasonable but it omits one of the big issues with NFSv2, which is synchronous writes. Those Sun NFS implementations were based on Sun's RPC system; the server was required not to reply until the write had been committed to stable storage. There was a mount option to disable this, but if you enabled it, it exposed you to data corruption. Certain vendors (SGI, if I recall correctly) at some point claimed their NFS was faster than Sun's, but it implemented asynchronous writes. This resulted in the expected arguments over protocol compliance and reliability vs. performance.

This phenomenon led to various hardware "NFS accelerator" solutions that put an NVRAM write cache in front of the disk in order to speed up synchronous writes. I believe Legato and the still-existing NetApp were based on such technology. Eventually the synchronous writes issue was resolved, possibly by NFSv3, though the details escape me.

>>smarks+od
There is a historical document by Olaf Kirch that addresses many aspects of the stateless design.

It also has some discussion of the indempotent replay cache that is also in the original article.

https://www.kernel.org/doc/ols/2006/ols2006v2-pages-59-72.pd...

>>chasil+cy
“Why NFS Sucks” (2006), picking on a protocol that was over 20 years old at that point. Also cites “The Unix-Haters Handbook” in the abstract. Two strikes against its credibility already.

However, I did skim the paper, and it seems halfway reasonable, so I suppose I should read the whole thing. Of course nothing is above criticism, and there are many valid criticisms of NFS; but leading with “sucks” is just lazy.

>>smarks+qz
As others have said I think the title was more clickbait-y. Olaf was the person who wrote the in-kernel NFS server so I think he at least appreciated NFS somewhat. The paper makes a few reasonable criticisms many of which are addressed now.

My favorite criticism from that paper is that NFS clients reused the source port so that the server can detect whether a new connection is the same client or not. This confuses stateful packet filtering on the network because both connections now have the same 5-tuple and packets on the new connection can look like out of window packets on the old connection. This can get connections blackholed depending on the network. This was fixed a few years ago in the Linux client for NFS v4.1, since that version of the protocol already has a different way to identify clients. Before this was fixed, EFS had to document a workaround.