From owner-freebsd-questions@FreeBSD.ORG Thu Aug 28 06:37:08 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 1C3967E2 for ; Thu, 28 Aug 2014 06:37:08 +0000 (UTC) Received: from sdf.lonestar.org (mx.sdf.org [192.94.73.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mx.sdf.org", Issuer "SDF.ORG" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id E4C5B1769 for ; Thu, 28 Aug 2014 06:37:07 +0000 (UTC) Received: from sdf.org (IDENT:bennett@sdf.lonestar.org [192.94.73.15]) by sdf.lonestar.org (8.14.8/8.14.5) with ESMTP id s7S6a7TB019899 (using TLSv1/SSLv3 with cipher DHE-RSA-AES256-GCM-SHA384 (256 bits) verified NO); Thu, 28 Aug 2014 06:36:07 GMT Received: (from bennett@localhost) by sdf.org (8.14.8/8.12.8/Submit) id s7S6a5OZ022667; Thu, 28 Aug 2014 01:36:05 -0500 (CDT) From: Scott Bennett Message-Id: <201408280636.s7S6a5OZ022667@sdf.org> Date: Thu, 28 Aug 2014 01:36:05 -0500 To: paul@kraus-haus.org Subject: Re: gvinum raid5 vs. ZFS raidz References: <201408020621.s726LsiA024208@sdf.org> <53DCDBE8.8060704@qeng-ho.org> <201408060556.s765uKJA026937@sdf.org> <53E1FF5F.1050500@qeng-ho.org> <201408070831.s778VhJc015365@sdf.org> <201408070936.s779akMv017524@sdf.org> <201408071106.s77B6JCI005742@sdf.org> <5B99AAB4-C8CB-45A9-A6F0-1F8B08221917@kraus-haus.org> <201408220940.s7M9e6pZ008296@sdf.org> <7971D6CA-AEE3-447D-8D09-8AC0B9CC6DBE@kraus-haus.org> <201408260641.s7Q6feBc004970@sdf.org> <9588077E-1198-45AF-8C4A-606C46C6E4F8@kraus-haus.org> In-Reply-To: <9588077E-1198-45AF-8C4A-606C46C6E4F8@kraus-haus.org> User-Agent: Heirloom mailx 12.4 7/29/08 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: freebsd-questions@freebsd.org, freebsd@qeng-ho.org, Trond.Endrestol@fagskolen.gjovik.no X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Aug 2014 06:37:08 -0000 Paul Kraus wrote: > On Aug 26, 2014, at 2:41, Scott Bennett wrote: > > Paul Kraus wrote: > >> On Aug 22, 2014, at 5:40, Scott Bennett wrote: > >>> What I'm seeing here is ~2 KB of errors out > >>> of ~1.1TB, which is an error rate (in bytes, not bits) of ~1.82e+09, and the As I caught and corrected before, the above should have said, "~1.82e-09". > >>> majority of the erroneous bytes I looked at had multibit errors. I consider > >>> that to be a huge change in the actual device error rates, specs be damned. > >> > >> That seems like a very high error rate. Is the drive reporting those errors or are they getting past the drive?s error correction and showing up as checksum errors in ZFS ? A drive that is throwing that many errors is clearly defective or dying. > > > > I'm not using ZFS yet. Once I get a couple more 2 TB drives, I'll give > > it a shot. > > The numbers are from running direct comparisons between the source file > > and the copy of it using cmp(1). In one case, I ran the cmp twice and got > > identical results, which I interpret as an indication that the errors are > > occurring during the writes to the target disk during the copying. > > Wow. That implies you are hitting a drive with a very high uncorrectable error rate since the drive did not report any errors and the data is corrupt. I have yet to run into one of those. How would an uncorrectable error be detected by the drive without any parity checking or hardware-implemented write-with-verify? Are you using any drives larger than 1 TB? If so, try copying a 1.1 TB file to one of them, and then trying comparing the copy against the original. Out of the three drives I could test that way, I got that kind of result on two every time I tried it. One of the two was a new Samsung (i.e., a Seagate), and the other was a refurbished Seagate supplied as a replacement under warranty. The third got a clean copy the first time and two bytes with single-bit errors on the second try. That one was also a refurbished Seagate provided under warranty. Scott Bennett, Comm. ASMELG, CFIAG ********************************************************************** * Internet: bennett at sdf.org *xor* bennett at freeshell.org * *--------------------------------------------------------------------* * "A well regulated and disciplined militia, is at all times a good * * objection to the introduction of that bane of all free governments * * -- a standing army." * * -- Gov. John Hancock, New York Journal, 28 January 1790 * **********************************************************************