From owner-freebsd-questions Wed Jul 4 23:33:45 2001 Delivered-To: freebsd-questions@freebsd.org Received: from mail1.rdc2.ab.home.com (mail1.rdc2.ab.home.com [24.64.2.48]) by hub.freebsd.org (Postfix) with ESMTP id 076BD37B405 for ; Wed, 4 Jul 2001 23:33:43 -0700 (PDT) (envelope-from rdh@best.com) Received: from best.com ([24.70.65.219]) by mail1.rdc2.ab.home.com (InterMail vM.4.01.03.20 201-229-121-120-20010223) with ESMTP id <20010705063342.COEF13758.mail1.rdc2.ab.home.com@best.com>; Wed, 4 Jul 2001 23:33:42 -0700 Received: (from rdh@localhost) by best.com (8.9.3/8.8.5) id AAA05295; Thu, 5 Jul 2001 00:33:41 -0600 (MDT) X-Authentication-Warning: ponoka.battleriver.com: rdh set sender to rdh@best.com using -f To: freebsd-questions@freebsd.org To: dnelson@emsphone.com, wmoran@iowna.com Subject: Re: SCSI bad block remapping References: <3B327713.46173EC5@iowna.com> <863d8curun.fsf@ponoka.battleriver.com> <20010704205514.A13653@dan.emsphone.com> From: Dale Hagglund Date: 05 Jul 2001 00:33:40 -0600 In-Reply-To: <20010704205514.A13653@dan.emsphone.com> (Dan Nelson's message of "Wed, 4 Jul 2001 20:55:15 -0500") Message-ID: <86pubfubp7.fsf@ponoka.battleriver.com> Lines: 28 User-Agent: Gnus/5.090003 (Oort Gnus v0.03) Emacs/20.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Dan Nelson writes: > In the last episode (Jul 04), Dale Hagglund said: > > (a) the disk might do remapping in fairly large chunks, even > > up to a track in size, and > ... The couple drives I've looked at map single blocks. ... > > (b) after remapping, the data in the remapped region is > > undefined. > I am extremely skeptical of this. If the data can be remapped, it > is remapped correctly (that's what all the ECC stuff is for). If it > cannot be remapped, an error is returned. Since this piqued my interest, I tracked down the horse's mouth. According to the the SCSI-3 Block Commands specification, when a REASSIGN BLOCKS command is issued the data contained in blocks being remapped may be modified. Also, the command can fail because it needs to remap a larger region than the one specified. However, from the documentation of AWRE and ARRE, it appears that blocks are reassigned automatically only if the drive firmware can recover the data. It looks like the upshot is that you can, as you suggested, turn on automatic sector remapping without fear of silent data loss. Dale. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message