Date: 05 Jul 2001 00:33:40 -0600 From: Dale Hagglund <rdh@best.com> To: dnelson@emsphone.com, wmoran@iowna.com Subject: Re: SCSI bad block remapping Message-ID: <86pubfubp7.fsf@ponoka.battleriver.com> In-Reply-To: <20010704205514.A13653@dan.emsphone.com> (Dan Nelson's message of "Wed, 4 Jul 2001 20:55:15 -0500") References: <3B327713.46173EC5@iowna.com> <863d8curun.fsf@ponoka.battleriver.com> <20010704205514.A13653@dan.emsphone.com>
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Dan Nelson <dnelson@emsphone.com> 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
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