From owner-freebsd-fs@FreeBSD.ORG Mon May 17 13:25:17 2004 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B060916A4CE for ; Mon, 17 May 2004 13:25:17 -0700 (PDT) Received: from sccrmhc12.comcast.net (sccrmhc12.comcast.net [204.127.202.56]) by mx1.FreeBSD.org (Postfix) with ESMTP id 14C2F43D31 for ; Mon, 17 May 2004 13:25:17 -0700 (PDT) (envelope-from julian@elischer.org) Received: from interjet.elischer.org ([24.7.73.28]) by comcast.net (sccrmhc12) with ESMTP id <2004051720251001200kvlere>; Mon, 17 May 2004 20:25:16 +0000 Received: from localhost (localhost.elischer.org [127.0.0.1]) by InterJet.elischer.org (8.9.1a/8.9.1) with ESMTP id NAA28634; Mon, 17 May 2004 13:25:07 -0700 (PDT) Date: Mon, 17 May 2004 13:25:04 -0700 (PDT) From: Julian Elischer To: Xin LI In-Reply-To: <20040517174836.GA983@frontfree.net> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: freebsd-fs@freebsd.org cc: Mikhail Teterin Subject: Re: QMail and SoftUpdates X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 May 2004 20:25:17 -0000 On Tue, 18 May 2004, Xin LI wrote: > On Mon, May 17, 2004 at 01:18:15PM -0400, Mikhail Teterin wrote: > > The link at > > > > http://cr.yp.to/qmail/faq/reliability.html#filesystems > > > > claims, using SoftUpdates for mailqueue is dangerous. Is that still > > true? Thanks! > > Yes, it is dangerous. Same is true for any journalling file systems, > which essentially does the same thing: delayed write of data/metadata. > > Delayed write will make it possible for the Operating System to group > several writes together and write them once, or at least, in a better > order in order to improve performance. However, for the mail case, once > it responds "250", then the remote peer is allowed to remove the message > from its queue. If the system crashes, and the data was not written into > disk, then your message is lost. > > Mounting your mailqueue slice with -noatime is a good idea, too. > > Please note that disabling SoftUpdates will drastically decrease write > performance on that slice. Of course, if your system often encounter > crash or power failure, it will be a good idea to disable it. Softupdates is NOT unsafe for this task IF the app does an fsync() before acknowldging the incoming mail. Fsync under Soft updates will not return until all data and metadata associated with the file has been written to disk. This will make the write as slow as a sync munted filesystem, but all other writes on the disk will proceeed at soft-updates speed. > > Cheers, > -- > Xin LI http://www.delphij.net/ > See complete headers for GPG key and other information. > >