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From: cdold@starfish.Convergent.COM (Clarence Dold)
Newsgroups: comp.unix.xenix
Subject: Re: QIC tape drive
Message-ID: <787@starfish.Convergent.COM>
Date: 28 Oct 88 23:00:45 GMT
References: <2011@ddsw1.MCS.COM>
Distribution: na
Organization: Convergent Technologies, San Jose, CA
Lines: 22

From article <2011@ddsw1.MCS.COM>, by karl@ddsw1.MCS.COM (Karl Denninger):
( refernce to Archive QIC tape drives...)
> 
> Now, we were under the impression that these drives had two gaps in the
> head, and that they at least checked for sanity in the data that was
> written.  It would appear that was a bad assumption, or that the particular
> failure mode the archive board experienced was undetectable by this
> operation.
> 
The problem is that the two-gap arrangement only verifies that magnetic 
fluctuations got from the Write gap to the Read gap intact.  
There is no verification that data got from the controller to the drive
intact.  There is an 8-bit data bus with no error check.
The gap trick is really only a media test.

> The moral?  ALWAYS check your tapes for readability, END TO END.

-- 
---
Clarence A Dold - cdold@starfish.Convergent.COM         (408) 435-5274
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