From owner-svn-doc-all@FreeBSD.ORG Wed Jan 16 04:30:25 2013 Return-Path: Delivered-To: svn-doc-all@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 27458A59; Wed, 16 Jan 2013 04:30:25 +0000 (UTC) (envelope-from eadler@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) by mx1.freebsd.org (Postfix) with ESMTP id 0183A6F6; Wed, 16 Jan 2013 04:30:25 +0000 (UTC) Received: from svn.freebsd.org (svn.FreeBSD.org [8.8.178.70]) by svn.freebsd.org (8.14.5/8.14.5) with ESMTP id r0G4UOdn075966; Wed, 16 Jan 2013 04:30:24 GMT (envelope-from eadler@svn.freebsd.org) Received: (from eadler@localhost) by svn.freebsd.org (8.14.5/8.14.5/Submit) id r0G4UONZ075965; Wed, 16 Jan 2013 04:30:24 GMT (envelope-from eadler@svn.freebsd.org) Message-Id: <201301160430.r0G4UONZ075965@svn.freebsd.org> From: Eitan Adler Date: Wed, 16 Jan 2013 04:30:24 +0000 (UTC) To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r40646 - head/en_US.ISO8859-1/books/faq X-SVN-Group: doc-head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-doc-all@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "SVN commit messages for the entire doc trees \(except for " user" , " projects" , and " translations" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Jan 2013 04:30:25 -0000 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" - - What about alternative layout policies for - directories? - - - - 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 - (total / fs_ncg) 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. - - &a.mckusick;, September 1998 - - - - How can I make the most of the data I see when my kernel panics?