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From: kevin@kosman.UUCP (Kevin O'Gorman)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Hard Disk questions
Message-ID: <803@kosman.UUCP>
Date: 1 Jul 89 16:38:35 GMT
References: <9186@phoenix.Princeton.EDU> <19995@cup.portal.com> <701@argon.UUCP>
Reply-To: kevin@kosman.UUCP (Root)
Followup-To: unix-pc.general
Organization: K.O.'s Manor - Vital Computer Systems, Oxnard, CA 93035
Lines: 16

In article <701@argon.UUCP> ebh@argon.UUCP (Ed Horch) writes:
>In article <19995@cup.portal.com> thad@cup.portal.com (Thad P Floryan) writes:
>>MB, formatted (UNIXPC, 16 sec/trk)	40.3			67.1
>>(ignoring the spare sec per track)
>
>What does the Unix PC do with that extra sector?  Is that how it
>remaps bad blocks?

Yes, the 17th sector is used for spares.

Note that a sector is half a logical block, so this arrangement makes some
sense: in the normal course of things, almost all blocks are read as two
consecutive sectors on the same track.

Also note, that when you specify bad blocks by logical block number, the
system pretty much has to assign alternates for both of the pysical sectors.