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Date:   Wed, 25 Nov 2020 14:31:38 -0500
From:   bfields <bfields@fieldses.org>
To:     Daire Byrne <daire@dneg.com>
Cc:     Trond Myklebust <trondmy@hammerspace.com>,
        linux-cachefs <linux-cachefs@redhat.com>,
        linux-nfs <linux-nfs@vger.kernel.org>
Subject: Re: Adventures in NFS re-exporting
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On Wed, Nov 25, 2020 at 05:14:51PM +0000, Daire Byrne wrote:
> Cool. I'm glad there are some notes for others to reference - this
> thread is now too long for any human to read. The only things I'd
> consider adding are:

Thanks, done.

> * re-export of NFSv4.0 filesystem can give input/output errors when the cache is dropped

Looking back at that thread....  I suspect that's just unfixable, so all
you can do is either use v4.1+ on the original server or 4.0+ on the
edge clients.  Or I wonder if it would help if there was some way to
tell the 4.0 client just to try special stateids instead of attempting
an open?

> * a weird interaction with nfs client readahead such that all reads
> are limited to the default 128k unless you manually increase it to
> match rsize.
>
> The only other thing I can offer are tips & tricks for doing this kind
> of thing over the WAN (vfs_cache_pressure, actimeo, nocto) and using
> fscache.

OK, I haven't tried to pick that out of the thread yet.

--b.