svn commit: r40646 - head/en_US.ISO8859-1/books/faq

[Eitan Adler]

Author: eadler
Date: Wed Jan 16 04:30:24 2013
New Revision: 40646
URL: http://svnweb.freebsd.org/changeset/doc/40646

Log:
  The alternate-directory-layout question has only historic value, there is no way
  to obtain reliable information from a modern HDD about cylinder groups.
  
  No objection from:	mckusick
  Approved by:		bcr (mentor)

Modified:
  head/en_US.ISO8859-1/books/faq/book.xml

Modified: head/en_US.ISO8859-1/books/faq/book.xml
==============================================================================
--- head/en_US.ISO8859-1/books/faq/book.xml	Tue Jan 15 20:53:43 2013	(r40645)
+++ head/en_US.ISO8859-1/books/faq/book.xml	Wed Jan 16 04:30:24 2013	(r40646)
@@ -8673,40 +8673,6 @@ hint.sio.7.irq="12"</programlisting>
       </qandaentry>
 
       <qandaentry>
-	<question id="alternate-directory-layout">
-	  <para>What about alternative layout policies for
-	    directories?</para>
-	</question>
-
-	<answer>
-	  <para>In answer to the question of alternative layout policies
-	    for directories, the scheme that is currently in use is
-	    unchanged from what I wrote in 1983.  I wrote that policy
-	    for the original fast file system, and never revisited it.
-	    It works well at keeping cylinder groups from filling up.
-	    As several of you have noted, it works poorly for find.
-	    Most file systems are created from archives that were
-	    created by a depth first search (aka ftw).  These
-	    directories end up being striped across the cylinder groups
-	    thus creating a worst possible scenario for future depth
-	    first searches.  If one knew the total number of directories
-	    to be created, the solution would be to create
-	    <literal>(total / fs_ncg)</literal> per cylinder
-	    group before moving on.  Obviously, one would have to create
-	    some heuristic to guess at this number.  Even using a small
-	    fixed number like say 10 would make an order of magnitude
-	    improvement.  To differentiate restores from normal
-	    operation (when the current algorithm is probably more
-	    sensible), you could use the clustering of up to 10 if they
-	    were all done within a ten second window.  Anyway, my
-	    conclusion is that this is an area ripe for
-	    experimentation.</para>
-
-	  <para>&a.mckusick;, September 1998</para>
-	</answer>
-      </qandaentry>
-
-      <qandaentry>
 	<question id="kernel-panic-troubleshooting">
 	  <para>How can I make the most of the data I see when my kernel
 	    panics?</para>