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Date:      Fri, 25 May 2001 06:17:33 +1000
From:      Greg Black <gjb@gbch.net>
To:        "Andresen,Jason R." <jandrese@mitre.org>
Cc:        void <float@firedrake.org>, hackers@FreeBSD.ORG
Subject:   Re: technical comparison 
Message-ID:  <nospam-990735453.93235@maxim.gbch.net>
In-Reply-To: <20010524082013.G88992-100000@nausicaa.mitre.org>  of Thu, 24 May 2001 08:24:29 -0400
References:  <20010524082013.G88992-100000@nausicaa.mitre.org> 

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"Andresen,Jason R." wrote:

| On Thu, 24 May 2001, void wrote:
| 
| > On Wed, May 23, 2001 at 09:20:51AM -0400, Andresen,Jason R. wrote:
| > >
| > > Why is knowing the file names cheating?  It is almost certain
| > > that the application will know the names of it's own files
| > > (and won't be grepping the entire directory every time it
| > > needs to find a file).
| >
| > With 60,000 files, that would have the application duplicating
| > 60,000 pieces of information that are stored by the operating system.
| > Operations like open() and unlink() still have to search the directory
| > to get the inode, so there isn't much incentive for an application to
| > do that, I think.
| 
| This still doesn't make sense to me.  It's not like the program is going
| to want to do a "find" on the directory every time it has some data it
| wants to put somewhere.  I think for the majority of the cases (I'm sure
| there are exceptions) an application program that wants to interact with
| files will know what filename it wants ahead of time.  This doesn't
| necessarily mean storing 60,000 filenames either, it could be something
| like:
| I have files fooX where X is a number from 00000 to 60000 in that
| directory.  I need to find a piece of information, so I run that
| information through a hash of some sort and determine that the file I want
| is number 23429, so I open that file.

And if this imaginary program is going to do that, it's equally
easy to use a multilevel directory structure and that will make
the life of all users of the system simpler.  There's no real
excuse for directories with millions (or even thousands) of
files.

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