From owner-freebsd-questions@FreeBSD.ORG Sat Dec 2 02:06:28 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 7C35F16A417 for ; Sat, 2 Dec 2006 02:06:28 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from smtpout.mac.com (smtpout.mac.com [17.250.248.184]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3106643C9D for ; Sat, 2 Dec 2006 02:06:10 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from mac.com (smtpin05-en2 [10.13.10.150]) by smtpout.mac.com (Xserve/8.12.11/smtpout14/MantshX 4.0) with ESMTP id kB226RK2006462; Fri, 1 Dec 2006 18:06:27 -0800 (PST) Received: from [17.214.13.96] (a17-214-13-96.apple.com [17.214.13.96]) (authenticated bits=0) by mac.com (Xserve/smtpin05/MantshX 4.0) with ESMTP id kB226P3k006442; Fri, 1 Dec 2006 18:06:25 -0800 (PST) In-Reply-To: <4570DA18.6070505@calarts.edu> References: <4570C4D6.5030708@calarts.edu> <671FF6D7-8F30-44DF-A8ED-2456E9B80170@mac.com> <4570DA18.6070505@calarts.edu> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <8ED90D8B-C688-4549-85DC-8BD1B8E54690@mac.com> Content-Transfer-Encoding: 7bit From: Chuck Swiger Date: Fri, 1 Dec 2006 18:06:24 -0800 To: Sean Murphy X-Mailer: Apple Mail (2.752.2) X-Brightmail-Tracker: AAAAAA== X-Brightmail-scanned: yes Cc: freebsd-questions@freebsd.org Subject: Re: Soft Updates Help 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: Sat, 02 Dec 2006 02:06:28 -0000 On Dec 1, 2006, at 5:42 PM, Sean Murphy wrote: > Thank you for your knowledge on this issue. I have a few > questions that I need your help to clarify. You are welcome, although knowledge can be a tricky thing. :-) > "Snapshots are taken via mksnap_ffs; some other tools like fsck or > dump also know how to create a snapshot." > > OK, so if I understand this correctly I do not have to > initially take a snapshot and update this snapshot manually. The > files system with soft updates does it correct? If the system is rebooted with a filesystem which is marked unclean, and if soft updates is enabled, then yes, the background fsck process will create a snapshot automatically, and not need manual intervention. > "Maybe. I think that softupdates is a win in almost all > circumstances from the standpoint of data consistency, short of > fully syncronous data & metadata updates." > > On this issue, if I do not have soft updates on does that > make it a fully synchronous file system? No. Take a look at the manpage for "mount", in particular the section on -o which discusses async, sync, and noasync. The latter is the default: " noasync Metadata I/O should be done synchronously, while data I/O should be done asynchronously. This is the default." > If the background fsck can't handle the inconsistencies it will > report this in the /var/log/messages correct? Then is the file > system unmounted because of the inconsistency to prevent data loss, > so I can run a manual fsck or does it stay mounted? It should fall back to running a foreground fsck instead, which might indeed require manual intervention, I believe. -- -Chuck