Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!purdue!decwrl!sgi!johnm
From: johnm@voltron.SGI.COM (Foosball Addict)
Newsgroups: comp.periphs
Subject: Re: Helical-Scan Query
Message-ID: <16266@sgi.SGI.COM>
Date: 21 Jun 88 23:18:04 GMT
References: <2648@usceast.UUCP> <11959@mimsy.UUCP> <1044@cfa.cfa.harvard.EDU>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics Inc, Mountain View, CA
Lines: 13

In article <1044@cfa.cfa.harvard.EDU>, wyatt@cfa.harvard.EDU (Bill Wyatt) writes:
> The Exabyte 8mm system uses a special head that DOES allow
> read-after-write.  Thus, blocks in error are caught and rewritten
> right away, some number of physical blocks down the tape.
  ^^^^^^^^^^

The Exabyte drive does a read after write to compare and if there are any
errors, it re-writes the date 11 blocks away. The reasoning is that typical
media flaws are horizontal in nature so the block the data is re-written
to is skewed off the line the error was detected.


johnm