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From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.)
Subject: Re: SCSI drive settings question
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References: <4hna0a$19q@stout.entertain.com> <pjm-1303960232070001@pjm.interlog.com>
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Organization: St. Peter's College, US
Date: Thu, 14 Mar 1996 14:10:09 GMT
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In article <pjm-1303960232070001@pjm.interlog.com>, pjm@cdromshop.com (Peter-John Maxwell) writes:
> Personally I would never contemplate turning parity checking off.
> When a parity error occurs, that track/sector is mapped out at the
> drive level without the controller even being aware of it.
> Basically the situation looks like this:
> an 8 bit byte:10101010 parity bit 0
> If any bit changes ie:
> 10101011 with the parity still at 0,
> You know that an error has occured in the storage of this byte.
> The drive will map any track/sectors where the errors occur to
> a "hidden" track/sector outside of the normally useable space on
> the HD.
I think there's some confusion here. What you're describing sounds like
Automatic Read Reallocation/Automatic Write Reallocation.
SCSI parity uses an additional data line in the cable to guard against
garbled transmission between initators and targets (more popularly known
as controllers and drives). It doesn't relate to storage of data on the
SCSI media. This is why you see it on non-storage SCSI devices such as
scanners and terminal servers.
Terry Kennedy Operations Manager, Academic Computing
terry@spcvxa.spc.edu St. Peter's College, Jersey City, NJ USA
+1 201 915 9381 (voice) +1 201 435-3662 (FAX)