In article <1992Sep25.014024.7807@fcom.cc.utah.edu>, terry@cs.weber.edu
(A Wizard of Earth C) writes:
quoted text
> In article <2dD802rK230r01@JUTS.ccc.amdahl.com> gab10@cd.amdahl.com
> (Gary A Browning) writes:
> >ISC 2.2.1 supports my Irwin Floppy Tape.  Since this came in the form
> as a 
> >new driver in its own patch, either the hooks to the scheduler were
> already
> >in the O/S or it is unnecessary  (An interesting note is that the
> original
> >distribution claimed to support many different Floppy Tapes but did
> not.
> >I'll bet Irwin supplied the driver to ISC.  The new driver makes not
> claims
> >at supporting any other manufacturers drives)
> 
> All SVR4 implementations support scheduling at realtime priorities --
> and

I wish it was SVR4.  It is only SVR3.2.

[ Stuff deleted ]
 
quoted text
> >The Irwin Floppy Tape drive is not a streamer.  It is necessary to preformat
> >the tapes into 512 bytes blocks.  Each block can be written without
> impacting
> >the block after it on the tape.  You can do random access operations.
> Think of
> >it as an incredibly slow floppy.  The point is that if the data for
> the
> >next block does not arrive in time, the drive simply has to
> reposition
> >before writing it. 
> 
> That "simply" is pretty time consuming... it sounds too much like "if
> the
> file has been migrated to tape, the tape robot 'simply' loads it back
> to
> physical disk".  I realize that it's not *quite* that time
> consuming... but
> still, one of the biggest wins of using a tape drive is that it's
> faster than
> using floppies; this generally means the ability to "stream" ...in
> other
> words, having the data ready to go *before* it's needed by the tape
> drive
> and not causing the to-tape latency to exceed the "streaming"
> threshold.  Or
> to put it another way, never stopping the tape when it's on a roll for
> lack
> of data or processing time.

Other important wins are the ability to hold more data and error correction.

I cannot remember exactly but I think when my drive was running under DOS
it is only running at about 22K a second.  This is very close the rate
the floppy runs I think.  

In any case, probably like most people who bought these floppy tape
drives, I thought cost was much more important than the speed.  When I
backup up DOS or ISC, I start it at night and then go to bed.  In fact,
formatting a new tape take 2.5 hours. From my point of view, any driver
that could access the 386BSD file system would be a win.  Even if it
seriously impacts other processes when it runs.

-- 
Gary Browning        | Exhilaration is that feeling you get just after a
                     | great idea hits you, and just before you realize
                     | what is wrong with it.