Re: Delays on "first" access to a NFS mount

[Neil Brown <neilb@suse.de>]

On Thursday March 8, bfields@fieldses.org wrote:
> On Thu, Mar 08, 2007 at 10:39:23AM +1100, Neil Brown wrote:
> > Imagine having hundreds of filesystems on some sort of library (a CD
> > library?) where each can be identified by a UUID which gets stored in
> > the fsid in the filehandle.
> > Imagine a simple extension to mountd so that a call-out were made when
> > an unknown filehandle arrived.  This callout could mount the required
> > filesystem and export it.  Maybe the library only allows 3 filesystems
> > to be mounted at a time, so it would unmount the lease-recently-used
> > one.
> 
> Maybe.  Is this practical?  Do we know of any cases of users doing this?

Someone once mentioned doing something vaguely like this... I don't
know the exact details.  It was mentioned in the context of the fsid
being too small to do a really good job.

I wonder if you can export autofs to get them mounted in the first
place..... 

> Do you block forever if you try to access 4 filesystems at once?  I
> dunno....

round-robin?  Sending lots of EINPROGRESS for one filesystem while the
others have a turn.


> 
> > I have often wanted to write a 'Linux commentary' that explains all
> > the hows and whys of things.  I even started some bits once (to help
> > me understand the VFS layer).  But Linux changes so fast that any
> > entry in such a commentary would be out-of-date before it was
> > written....
> 
> And there's a lot to document.  I mean, look:
> 
> 	http://www.oreilly.com/catalog/understandlni/
> 
> Just over a thousand pages, just covering the kernel networking code
> (and only some of it at that).  Maybe they just lost the forest for the
> trees, but still, yipes.

Is there really a market for that sort of book?  Maybe we should write
"Understanding Linux NFS" in our spare time .... oh wait, we don't
have any spare time.  Maybe in a couple of decades when I retire:-)

NeilBrown

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