From owner-freebsd-geom@FreeBSD.ORG Mon Jul 13 08:30:03 2009 Return-Path: Delivered-To: freebsd-geom@hub.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3DAE81065670 for ; Mon, 13 Jul 2009 08:30:03 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id 2C2E28FC1A for ; Mon, 13 Jul 2009 08:30:03 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1]) by freefall.freebsd.org (8.14.3/8.14.3) with ESMTP id n6D8U3xA016733 for ; Mon, 13 Jul 2009 08:30:03 GMT (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.14.3/8.14.3/Submit) id n6D8U2gf016730; Mon, 13 Jul 2009 08:30:02 GMT (envelope-from gnats) Date: Mon, 13 Jul 2009 08:30:02 GMT Message-Id: <200907130830.n6D8U2gf016730@freefall.freebsd.org> To: freebsd-geom@FreeBSD.org From: Dan Naumov Cc: Subject: Re: kern/121481: [gmirror] data rot on disk with gmirror X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: Dan Naumov List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Jul 2009 08:30:03 -0000 The following reply was made to PR kern/121481; it has been noted by GNATS. From: Dan Naumov To: bug-followup@FreeBSD.org, zdbs@lif.de Cc: Subject: Re: kern/121481: [gmirror] data rot on disk with gmirror Date: Mon, 13 Jul 2009 11:23:32 +0300 Bernard, while I understand your frustration, you are barking up the wrong tree. RAID offers protection against very specific kinds of disk failure and does not offer any kind of protection against bit rot. I want to emphasize that this is not a FreeBSD issue, but a RAID issue in general and you will run into exact same limitations if you try raid on Linux or Windows or hardware raid from any hardware vendor. For another example of a fault that RAID mirror will NOT protect you or even warn you against, is your disk/raid controller going berserk and writing garbage to the mirror or one of it's member disks. If you are happy with just getting a warning when file(s) somewhere are silently getting corrupted, this can easily be easily implemented with existing tools: there are plenty of checksumming utilities you can use to checksum your datasets and you could set up a cronjob to have the utility run a check of your files against a known hash database and list all the files (if any) that have changed, mailing you the output. When properly configured, this can also help with intrusion detection, as it can help detecting all new or changed files on the system :) However, if you require not only a warning, but also automatic recovery and healing from such corruption, your only option is ZFS and if you have evaluated the state of ZFS in FreeBSD and concluded that it's not mature enough for your needs, then your only other option is Solaris. - Sincerely, Dan Naumov