From owner-freebsd-questions@FreeBSD.ORG Mon Jul 10 12:55:08 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E294D16A4DD for ; Mon, 10 Jul 2006 12:55:08 +0000 (UTC) (envelope-from jerlique@webscene.com.au) Received: from bang.esc.net.au (mx1.esc.net.au [203.25.185.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id D147743D67 for ; Mon, 10 Jul 2006 12:54:53 +0000 (GMT) (envelope-from jerlique@webscene.com.au) Received: from localhost (localhost [127.0.0.1]) by bang.esc.net.au (Postfix) with ESMTP id 7C0FF5A69DE; Mon, 10 Jul 2006 22:24:52 +0930 (CST) Received: from bang.esc.net.au ([127.0.0.1]) by localhost (bang.esc.net.au [127.0.0.1:10024]) (amavisd-new) with ESMTP id 56900-04; Mon, 10 Jul 2006 22:24:50 +0930 (CST) Received: from WKSTN501 (lnk6.adl5.adsl.esc.net.au [210.9.186.6]) by bang.esc.net.au (Postfix) with ESMTP id 7B2135A695F; Mon, 10 Jul 2006 22:24:50 +0930 (CST) From: "Jerlique Bahn" To: "'Chuck Swiger'" Date: Mon, 10 Jul 2006 22:24:47 +0930 Message-ID: <00a101c6a420$064769d0$0101a8c0@WKSTN501> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 In-Reply-To: <44B0DE66.3080406@mac.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 Thread-Index: AcajRQnaeUEQdpEsQuiKBzDcG1BwEgA1v2ng X-Virus-Scanned: by amavisd-new Cc: freebsd-questions@freebsd.org Subject: RE: lost+found 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: Mon, 10 Jul 2006 12:55:09 -0000 Hello Chuck, > Jerlique Bahn wrote: > > If I pull the power on my server whilst its doing heavy IO, should I get > > files in lost+found if my raid card has battery backed cache? > > Yes, it's still possible. > > The cache on the RAID card will be flushed OK, but any in-process > operations by live processes will be interrupted in the middle if the OS > goes away. While some operations are atomic (things like unlink or move), > simply writing pieces out is not... Ok, this is contrary to what was my belief, but I guess it really does makes sense. Eg Suppose we are talking about writing a 1gb file. This obviously needs to be written to the disk, and not stored in cache. So can you explain the process of ufs writing the file, and what ends up in lost+found if the server is rebooted part way through eg say we are 3/4 of the way through writing the file before reboot. Or better still are there any "semi-technical" white papers/web-pages which could explain this, and under what circumstances lost+found is used. > > I would like to also know how to turn off (or check) caching on the > physical > > disk itself. > > smartmontools port? sysctl hw.ata.wc...? Sorry I should have mentioned I'm using SCSI disks behind a raid card ;) Thanks for your comments! JB