From owner-freebsd-questions@FreeBSD.ORG Mon Jan 28 22:49:19 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id EE898D33 for ; Mon, 28 Jan 2013 22:49:19 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: from mail-ve0-f177.google.com (mail-ve0-f177.google.com [209.85.128.177]) by mx1.freebsd.org (Postfix) with ESMTP id A7E3A1E2 for ; Mon, 28 Jan 2013 22:49:19 +0000 (UTC) Received: by mail-ve0-f177.google.com with SMTP id m1so1726497ves.22 for ; Mon, 28 Jan 2013 14:49:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:subject:mime-version:content-type:from:in-reply-to:date :content-transfer-encoding:message-id:references:to:x-mailer :x-gm-message-state; bh=NZzLE7eT3/c3t5t1GqWzEzoQuJL3/4WlhfQ8qIjskn4=; b=QjKYjLfLszBojjvxjHmhw5q+cy6oavjtXJ7VbylFqqEHaiGKfYWPBv1Nvah5uAW3zh jof/9LvWkGeQxyaNlIlHcl1/qrPRMsc8VbS+V5ASOWJQ+6Jy0BsgORYg2NnsnKhSolEQ lyVaPfRUnygqJrnH2GlZ5Yp3ar9/YgDZzcxNZKyol1/7N03jMZdKg0+tv1iuplLUZFxE +Z8+ijEyFMHbvYVpAfQ96FNhIvMZzKFfJIP3OHY64SirfK2OoWeQpmXlQBnLk5NOmT2w wWD+j9WUdpZE2pIOtaOemg1k76r6Pj+7dTjuLd9U/QXA+yEHkHjxe9jYRkPdjFcFEwaU BVCw== X-Received: by 10.52.95.233 with SMTP id dn9mr14602260vdb.88.1359413358522; Mon, 28 Jan 2013 14:49:18 -0800 (PST) Received: from mini1.kraus-haus.org ([96.236.21.119]) by mx.google.com with ESMTPS id bj15sm7225590vdc.7.2013.01.28.14.49.16 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 28 Jan 2013 14:49:17 -0800 (PST) Subject: Re: Software raid VS hardware raid Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: text/plain; charset=us-ascii From: Paul Kraus In-Reply-To: <5106E301.4070707@itlegion.ru> Date: Mon, 28 Jan 2013 17:49:15 -0500 Content-Transfer-Encoding: quoted-printable Message-Id: <5C5F6EE2-5744-48B8-B4D9-DB9E19A5FCC0@kraus-haus.org> References: <5106E301.4070707@itlegion.ru> To: FreeBSD Mailing List X-Mailer: Apple Mail (2.1085) X-Gm-Message-State: ALoCoQm/AOXgAqquAANCBImr0LyjDUzkd6LYhqUgvRSpKg9RJGfYMBL1/MgvsZTU4jDgedQHeIQq X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Jan 2013 22:49:20 -0000 On Jan 28, 2013, at 3:43 PM, Artem Kuchin wrote: > I have to made a decision on choosing a dedicated server. > The problem i see is that while i can find very affordable and good = options they do not > provide hardware raid or even if they do it is not the best hardware = for freebsd. I prefer SW RAID, specifically ZFS, for two very large reasons: 1) Visibility: =46rom the OS layer you have very good visibility into = the health of the RAID set and the underlying drives. All of the lower = end HW RAID solutions I have seen require proprietary software to = "manage" the RAID configuration, usually from the physical system's BIOS = layer. Finding good OS layer software to monitor the RAID and the drives = has been very painful. If you don't know you have a failure, then you = can't do anything about it and when you have a second failure you lose = data. Running a HW RAID system and not being able to issue a simple = command from the OS and see the status of the RAID scares me. 2) Error Detection and Correction: HW RAID relies on the drives to = report read and write errors. With UNCORRECTABLE error rates of 10^-14 = and 10^-15 and LARGE (1 TB plus) drives you are almost guaranteed to = statistically run into UNCORRECTABLE errors over the life of a typical = drive. ZFS has end to end checksums and can detect a single bad bit from = a drive, if the set is redundant it can recreate the correct data and = re-write it, effectively correcting the bad data on disk. NOTE: Larger, more expensive HW RAID systems address both of the above = issues, but at a much higher cost in terms of money and management = overhead. DISCLAIMER: I have been managing mission critical, cannot afford to lose = it data under ZFS for over 5 years, with no loss of data (even with some = horribly unreliable low cost HW RAID systems under the ZFS layer... if = we had not used ZFS we would have lost data multiple times). =20 -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company