From owner-freebsd-questions@FreeBSD.ORG Fri May 21 07:14:24 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 57AD91065670 for ; Fri, 21 May 2010 07:14:24 +0000 (UTC) (envelope-from lists@eitanadler.com) Received: from mail-iw0-f182.google.com (mail-iw0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id 2B92D8FC19 for ; Fri, 21 May 2010 07:14:23 +0000 (UTC) Received: by iwn5 with SMTP id 5so894664iwn.13 for ; Fri, 21 May 2010 00:14:23 -0700 (PDT) Received: by 10.231.125.129 with SMTP id y1mr785926ibr.96.1274426063140; Fri, 21 May 2010 00:14:23 -0700 (PDT) MIME-Version: 1.0 Received: by 10.231.148.136 with HTTP; Fri, 21 May 2010 00:14:03 -0700 (PDT) In-Reply-To: <4BF10F3D.2070207@gmx.com> References: <4BE84825.9060005@gmx.com> <1a7012fe7affe8caf4263d4d2c385614.squirrel@whipp.no-ip.org> <4BF10F3D.2070207@gmx.com> From: Eitan Adler Date: Fri, 21 May 2010 10:14:03 +0300 Message-ID: To: Nikos Vassiliadis Content-Type: text/plain; charset=UTF-8 Cc: crwhipp@gmail.com, freebsd-questions@freebsd.org Subject: Re: File system X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 May 2010 07:14:24 -0000 gjournal will replay all write attempts > (metadata and data) before the failure, so you should be relatively > sure that all writes are done correctly. As I understand it journals work by writing to disk a log of all the changes that have to be made - waits for confirmation that it wrote the data - and then attempts to make those changes. If after the confirmation there is a crash the log file is replayed. Certain virtual machines will report to the OS that it wrote the data to disk before it actually does so. In that case journaling doesn't actually help as the log file is still not on some form of stable storage. -- Eitan Adler