From owner-freebsd-questions@FreeBSD.ORG Tue May 11 23:02:19 2010 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id DD507106566C for ; Tue, 11 May 2010 23:02:19 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout028.mac.com (asmtpout028.mac.com [17.148.16.103]) by mx1.freebsd.org (Postfix) with ESMTP id C58248FC18 for ; Tue, 11 May 2010 23:02:19 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii Received: from cswiger1.apple.com ([17.209.4.71]) by asmtp028.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0L2A00I802NIRW90@asmtp028.mac.com> for questions@freebsd.org; Tue, 11 May 2010 16:02:07 -0700 (PDT) X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 ipscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx engine=6.0.2-1004200000 definitions=main-1005110150 X-Proofpoint-Virus-Version: vendor=fsecure engine=1.12.8161:2.4.5,1.2.40,4.0.166 definitions=2010-05-11_06:2010-02-06, 2010-05-11, 2010-05-11 signatures=0 From: Chuck Swiger In-reply-to: <914660.33515.qm@web111619.mail.gq1.yahoo.com> Date: Tue, 11 May 2010 16:02:06 -0700 Message-id: <82D375DD-9641-4602-93A9-5D84BB55688E@mac.com> References: <914660.33515.qm@web111619.mail.gq1.yahoo.com> To: George Sanders X-Mailer: Apple Mail (2.1078) Cc: questions@freebsd.org Subject: Re: dumping a raid member with 'dd' for insurance... 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: Tue, 11 May 2010 23:02:19 -0000 Hi-- On May 11, 2010, at 3:35 PM, George Sanders wrote: > [ ... ] > I am planning on attaching each individual member of the raid5 array to a test FreeBSD system, and run: > > dd if=/dev/ad1 of=/data/disk/image.file > > Two questions: > > - is that a complete 'dd' command, or do I need to specify "bs=xxx" and "count=xxx" ? What you've suggested should work as-is. Adding the count option isn't useful, but specifying a bs of 64k or larger will considerably speed up the process of copying the data. Since you're dealing with a failed array and it's possible some of the disks might have errors when read, using conv=noerror might also be a good idea. > - is there any chance that simply booting with this drive attached to the system, and running a 'dd' like this, will somehow alter the contents or "touch" the array member in any way ? What I have described above appears to be a completely read-only process, but I'd like to make sure there aren't ANY bits that FreeBSD will write to this disk ... Many disks have a write-protect jumper which you can use to make sure no changes get written. Regards, -- -Chuck