Date: Mon, 27 Nov 1995 01:22:46 +0000 () From: Michael Smith <msmith@atrad.adelaide.edu.au> To: terry@lambert.org (Terry Lambert) Cc: msmith@atrad.adelaide.edu.au, terry@lambert.org, hasty@rah.star-gate.com, hackers@FreeBSD.org Subject: Re: Help! I got a bad block.... Message-ID: <199511270122.BAA02417@genesis.atrad.adelaide.edu.au> In-Reply-To: <199511241815.LAA09932@phaeton.artisoft.com> from "Terry Lambert" at Nov 24, 95 11:15:13 am
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Terry Lambert stands accused of saying: > > > > If the replacement sectors are otherwise exposed as usable data sectors, > > > turning it on would be Bad(tm) if you have already stored data on the > > > drive. > > > > I don't _think_ anyone would be that stupid. > > I see you've never owned a WD1007 ESDI controller. 8-). Yes, actually. I stopped using them and went with the Adaptec 232x controllers after I got sick of the wdformat program. > I don't buy the "on a bad day argument". I can't see how a good sector > could be incorrectly marked bad, unless you have the driver cooperate in > the marking and blow the driver programming. If the drive has forwarding enabled, and for one reason or another (thermal, LF vibrations, wrong phase of the moon) has problems writing a sector, it'll forward it, and you'll lose the original. > I believe you can clear the sectors that have been remapped in any case > by issuing SCSI commands. If nothing else, you can re low-level format > the drive. As previously observed, some drives let you do this, some don't. > I think that the device ought to have an "implied" media perfection > layer that causes the remapping to be turned on by default when FreeBSD > is installed. Hell, I think it ought to be turned on when Win95 is > installed (it isn't, in case you were wondering). Forwarding doesn't do all the job, as far as media perfection is concerned - once you run out of spare sectors, you're screwed. I've met a few drives that appear to have lost their marbles when they ran out, and others that just start to report errors, despite the fact that forwarding is enabled. Unless you can positively identify the drive, determine the number of _free_ spare sectors, and make a judgement call on how many you're likely to use in a given uptime period, you still need a higher layer to catch the failure case. > Terry Lambert -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 041-122-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] "Who does BSD?" "We do Chucky, we do." [[
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