Why do we worry? And other embarrassing questions

Bob Snively Bob.Snively at Eng.Sun.COM
Tue Nov 22 22:18:22 PST 1994


I have been told on good authority that all "modern" (post-1991) tape drives
perform WRITE IMMEDIATE and buffered writing in a manner that 
does not require an ECA or ACA recovery operation.

It turns out that all the manufacturers found that people were
having so much trouble finding host adapters and software that
would perform ACA/ECA that they fixed their architecture such
that it was no longer needed.  As a result, they do strange things
like counting tach pulses and other early warning operations to
decrease buffer size or shut down buffering far enough before the
end of a tape to guarantee they will never indicate EOM with data
remaining in the buffer.

I assume that each representative at the meetings felt this ACA/ECA
question applied to some other tape and therefore might be a
legitimate concern.  This letter is a test to see if there are
any real "modern" tape drives that truly require and use ACA/ECA and if
there are any "modern" systems that use and require ACA/ECA.

Robert Snively
Sun Microsystems Computer Company
Mail Stop UMPK 12-204
2550 Garcia Avenue
Mountain View
California 94043-1100

Phone:		(415) 786-6694
FAX:		(415) 786-6458
e-mail:		bob.snively at Eng.sun.com




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