From owner-svn-src-head@freebsd.org Fri Feb 9 22:23:11 2018 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5AC92F07110; Fri, 9 Feb 2018 22:23:11 +0000 (UTC) (envelope-from mckusick@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E48BB7C5A7; Fri, 9 Feb 2018 22:23:10 +0000 (UTC) (envelope-from mckusick@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id DB0722E32; Fri, 9 Feb 2018 22:23:10 +0000 (UTC) (envelope-from mckusick@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w19MNAl4021794; Fri, 9 Feb 2018 22:23:10 GMT (envelope-from mckusick@FreeBSD.org) Received: (from mckusick@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w19MNAr1021793; Fri, 9 Feb 2018 22:23:10 GMT (envelope-from mckusick@FreeBSD.org) Message-Id: <201802092223.w19MNAr1021793@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mckusick set sender to mckusick@FreeBSD.org using -f From: Kirk McKusick Date: Fri, 9 Feb 2018 22:23:10 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r329087 - head/tools/diag/prtblknos X-SVN-Group: head X-SVN-Commit-Author: mckusick X-SVN-Commit-Paths: head/tools/diag/prtblknos X-SVN-Commit-Revision: 329087 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 09 Feb 2018 22:23:11 -0000 Author: mckusick Date: Fri Feb 9 22:23:10 2018 New Revision: 329087 URL: https://svnweb.freebsd.org/changeset/base/329087 Log: Add an explanation of the block size units output by prtblknos. Suggested by: Ravi Pokala (rpokala@) Modified: head/tools/diag/prtblknos/README Modified: head/tools/diag/prtblknos/README ============================================================================== --- head/tools/diag/prtblknos/README Fri Feb 9 21:51:08 2018 (r329086) +++ head/tools/diag/prtblknos/README Fri Feb 9 22:23:10 2018 (r329087) @@ -27,5 +27,22 @@ The distance metric is the size of the gap from the en previous set of blocks to the beginning of the next set of blocks. Short distances are desirable. +The logical block numbers (lbn above) describe filesystem-block +size blocks which by today's default is 32Kb. + +The physical block numbers (blkno above) describe the smallest piece +of disk space that an inode can reference which is a filesystem +fragment. Since the default size for fragments today is 4Kb, the +physical block numbers reference 4Kb blocks. The distances listed +above are also in physical block size units. Thus a distance of 8 +means a separation of just one 32Kb block. For example lbn 11, ends +at 3217895, the 32Kb first level indirect immediately follows it at +3217896-3217903, and lbn 12 starts distance 8 after lbn 11 immediately +after the indirect block at 3217904. + +If you were to create a filesystem with the fragment size equal to +half the block size (say 32Kb blocks with 16Kb fragments) then the +physical block numbers listed would be 16Kb in size. + Marshall Kirk McKusick January 19, 2018