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Date:      Tue, 8 Oct 2002 21:08:00 +0200 (CEST)
From:      Oliver Fromme <olli@secnetix.de>
To:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: Mount option "nomtime"?
Message-ID:  <200210081908.g98J809u055938@lurza.secnetix.de>
In-Reply-To: <20021008183835.GA65525@falcon.midgard.homeip.net>

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Erik Trulsson <ertr1013@student.uu.se> wrote:
 > On Tue, Oct 08, 2002 at 07:17:59PM +0200, Oliver Fromme wrote:
 > > [...]
 > > For example, updating of mtimes is not neccessary on a
 > > file system that contains a news spool, or the content of
 > > a web cache, or similar transient data.  Disabling those
 > > updates might prevent quite some superfluous overhead.
 > 
 > Since I suspect that most writes occur when you are first creating the
 > file and that modifications in existing files are fairly uncommon I
 > think any performance gains would be quite minor.

I should have been more specific in my examples.  Sorry.

Think about INN with using cycbuffers (CNFS) when storing
news articles (which is pretty standard on fullfeed news
servers).  Those cycbuffers are a bunch of large files.
Their size never changes, but a lot of data is written to
them all the time.  The same goes for the overview data
when using the so-called buffindexed storage.  INN itself
does not need the mtime information of the buffer files.

Another example would be "oops", which is a very fast,
lightweight web proxy.  It uses cyclic buffer files to
store the cached data, similar to INN's CNFS.

I think in the above cases, a "nomtime" option would indeed
save some unnecessary overhead.

Of course, I agree that it won't buy you much in the case
of "normal" file creation or appending to existing files.
But that's not the kind of scenario I have in mind.

Regards
   Oliver

-- 
Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

"All that we see or seem is just a dream within a dream" (E. A. Poe)

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