Re: which ioctls matter across filesystems

From: Steve French
Date: Fri Apr 29 2005 - 16:30:20 EST

Trond Myklebust wrote:

I think what the IETF NFS working group rather needs right now is an
advocate that is willing to stand up and demonstrate why protocol
support for inotify-style callbacks would be a more scalable solution
than a solution based on a combination of GETATTR polling and read
delegations (essentially the same thing as CIFS' op-locks) for

I agree.

The current research (see which
has uses real-life on-the-wire traffic actually leans more towards the
GETATTR solution. That research was based on a set of anonymous tcpdump
traces taken at Harvard University, though, so it reflects the traffic
in a typical university environment. It may be that other use-cases
exist that favour the inotify callbacks case.

Very interesting, I had not seen that. FYI - There are many years of real world experience on the current transact2 notify (it is deployed in some form on most clients) but I don't know whether one of the NAS storage companies or researchers has done a good research paper on this topic - although there is no lack of customer traces in SPEC and SNIA.

My gut reaction is that as
1) directory size increases (number of files per directory)
2) change rate goes down

(both of which could be client heuristics) the notify mechanism (on the directory, or parent directory) is much better, but with small directories and more frequent changes the getattr (Transact2 QueryPathinfo) approach wins. There is no one-size-fits-all that covers both cases.
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