From owner-freebsd-questions@FreeBSD.ORG Sun Jan 2 20:30:49 2011 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 2C7F61065672 for ; Sun, 2 Jan 2011 20:30:49 +0000 (UTC) (envelope-from gull@gull.us) Received: from mail-ew0-f54.google.com (mail-ew0-f54.google.com [209.85.215.54]) by mx1.freebsd.org (Postfix) with ESMTP id C22708FC12 for ; Sun, 2 Jan 2011 20:30:48 +0000 (UTC) Received: by ewy24 with SMTP id 24so6106060ewy.13 for ; Sun, 02 Jan 2011 12:30:47 -0800 (PST) MIME-Version: 1.0 Received: by 10.14.123.68 with SMTP id u44mr12759724eeh.21.1294000247783; Sun, 02 Jan 2011 12:30:47 -0800 (PST) Received: by 10.14.124.148 with HTTP; Sun, 2 Jan 2011 12:30:47 -0800 (PST) X-Originating-IP: [64.81.163.112] In-Reply-To: <4D20D872.3020400@speakeasy.net> References: <4D20D872.3020400@speakeasy.net> Date: Sun, 2 Jan 2011 12:30:47 -0800 Message-ID: From: David Brodbeck To: freebsd general questions Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: Half a Mirror Backup 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: Sun, 02 Jan 2011 20:30:49 -0000 On Sun, Jan 2, 2011 at 11:56 AM, Jason C. Wells wrote: > Is using one half of a mirror as a backup a good/bad idea? > > I was thinking of rotating drives on a periodic basis as a back up method= . > =A0You'd get the backup instantly, but rebuilding the mirror with the inc= oming > drive would take a little time and leave you vulnerable to a small loss o= f > data if a disk failed while the mirror was rebuilding. Besides the problem you mention, you'll have a pretty sizable performance hit while the mirror is being rebuilt. Also, keep in mind that the most likely time for a second drive to fail is during a rebuild, since the rebuild forces a read from every sector. I think I would use rsync or dump instead, although I have to admit the rotating mirror idea is clever.