From owner-freebsd-hackers@freebsd.org Thu Jul 5 01:09:23 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 62971103161D for ; Thu, 5 Jul 2018 01:09:23 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from hz.grosbein.net (unknown [IPv6:2a01:4f8:d12:604::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "hz.grosbein.net", Issuer "hz.grosbein.net" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id DD8297D3A4 for ; Thu, 5 Jul 2018 01:09:22 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from eg.sd.rdtc.ru (root@eg.sd.rdtc.ru [62.231.161.221] (may be forged)) by hz.grosbein.net (8.15.2/8.15.2) with ESMTPS id w6519GNt012473 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 5 Jul 2018 03:09:16 +0200 (CEST) (envelope-from eugen@grosbein.net) X-Envelope-From: eugen@grosbein.net X-Envelope-To: george+freebsd@m5p.com Received: from [10.58.0.4] ([10.58.0.4]) by eg.sd.rdtc.ru (8.15.2/8.15.2) with ESMTPS id w6519C79079686 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Thu, 5 Jul 2018 08:09:12 +0700 (+07) (envelope-from eugen@grosbein.net) Subject: Re: Confusing smartd messages To: George Mitchell , freebsd-hackers@freebsd.org References: <5B3D6975.2060508@grosbein.net> <17c1cb78-f2f0-ff13-6425-8ac634ddaa56@m5p.com> From: Eugene Grosbein Message-ID: <5B3D6FB3.5010908@grosbein.net> Date: Thu, 5 Jul 2018 08:09:07 +0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <17c1cb78-f2f0-ff13-6425-8ac634ddaa56@m5p.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=2.2 required=5.0 tests=BAYES_00, LOCAL_FROM, RDNS_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.1 X-Spam-Report: * -0.0 SPF_PASS SPF: sender matches SPF record * -2.3 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * 2.6 LOCAL_FROM From my domains * 1.9 RDNS_NONE Delivered to internal network by a host with no rDNS X-Spam-Level: ** X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on hz.grosbein.net X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 Jul 2018 01:09:23 -0000 05.07.2018 7:54, George Mitchell write: >> First step is running zpool scrub or even replace the disk and run "dd if=/dev/zero of=/dev/ada1". >> [...] > > I'll start with zpool scrub. What's the magic command (if any) to > force a rewrite of the sectors? -- George Modern HDDs are embedded computers theyselves with their own CPU, RAM, flash memory and special operating system (firmware) running inside. They have spare load of generally unused and hidden sectors also. When firmware sees write error due to really bad spot on magnetic part of disk making a sector "bad", it performs a remap by means of internal translation table for LBAs to use one of hidden sectors instead of bad one. And until the amount of hidden sectors is not exhausted (there are can be over a thousand of them), the disk keeps running nearly fine. Sometimes the sector just gets wrong checksum written due to power failure, hence read errors due to "mismatched" checksum. Overwrite corrects such "soft bad" error without need to remap. Eugene P.S. your smtp server (MX) rejects my direct mail to you with "550 5.7.1 Access denied" errors.