Re: How long should a dd take

From	Jean-David Beyer <jeandavid8@verizon.net>
Newsgroups	comp.os.linux.misc
Subject	Re: How long should a dd take
Date	2020-03-27 21:35 -0400
Organization	NewsGuy.com
Message-ID	<r5m9li01ipp@news1.newsguy.com> (permalink)
References	(11 earlier) <r5le29$h96$1@dont-email.me> <r5lgq8$6st$1@dont-email.me> <L_udnQHeMI7Fw-PDnZ2dnUU7-ffNnZ2d@giganews.com> <r5lpm102m4h@news2.newsguy.com> <r5lq76$1v0$3@dont-email.me>

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On 3/27/20 5:12 PM, Rich wrote:
> Jean-David Beyer <jeandavid8@verizon.net> wrote:
>> On 3/27/20 4:13 PM, Robert Heller wrote:
>>> With the default setting for bs, a very long time.  dd's defaults 
>>> are mostly wrong much of the time.
>>
>> It looks that the defaults were chosen at the time of DEC PDP-11 
>> machines whose disk drives were demarcated into blocks (512 bytes) 
>> tracks (10 or 19) and cylinders.
> 
> What block sizes did tape drives of the DEC PDP-11 era (predates my 
> time) support?  Was 512 bytes possibly also chosen as the default 
> because early tape hardware required 512 byte blocks?
> 

I am not sure. DECTape drives could modify individual records on the
tape; I.e., tape blocks were addressable. I never met any other tape
drive that could do that. I think they picked 512byte block size there
too to be compatible with their disk drives. I never used a DECTape, so
I may be mistaken about this.

-- 
  .~.  Jean-David Beyer
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 /( )\ Shrewsbury, New Jersey
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How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-24 11:43 +0000
  Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-24 13:13 +0100
    Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-24 16:37 +0000
      Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-24 12:25 -0500
        Re: How long should a dd take Eli the Bearded <*@eli.users.panix.com> - 2020-03-24 18:12 +0000
        Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-25 04:05 +0000
          Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-25 21:25 +0100
            Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-26 12:25 +0000
              Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-26 13:52 +0100
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-26 15:43 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-26 15:55 +0000
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-26 18:36 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-26 18:53 +0000
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-27 08:09 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-27 10:00 +0000
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-27 10:15 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-27 15:58 +0000
                Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-27 13:43 -0400
                Re: How long should a dd take Roger Blake <rogblake@iname.invalid> - 2020-03-27 22:45 +0000
                Re: How long should a dd take ant@zimage.comANT (Ant) - 2020-03-28 17:00 -0500
                Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-27 14:11 +0100
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-27 13:49 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-27 17:44 +0000
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-27 18:31 +0000
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-27 19:58 +0000
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-27 20:14 +0000
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-27 15:13 -0500
                Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-27 21:47 +0100
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-28 05:30 +0000
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-28 07:33 -0500
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-28 13:41 +0000
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-28 09:47 -0500
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-28 17:48 +0000
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-28 14:27 -0500
                Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-28 22:22 +0100
                Re: How long should a dd take The Natural Philosopher <tnp@invalid.invalid> - 2020-03-29 06:41 +0100
                Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-27 17:02 -0400
                Re: How long should a dd take Rich <rich@example.invalid> - 2020-03-27 21:12 +0000
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-27 20:35 -0500
                Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-27 21:35 -0400
                Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-27 20:35 -0500
                Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-26 22:03 +0100
                Re: How long should a dd take "Anonymous Remailer (austria)" <mixmaster@remailer.privacy.at> - 2020-03-27 16:01 +0100
      Re: How long should a dd take Roger Blake <rogblake@iname.invalid> - 2020-03-24 19:59 +0000
  Re: How long should a dd take Marc Haber <mh+usenetspam1118@zugschl.us> - 2020-03-24 13:22 +0100
  Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-24 08:21 -0500
    Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-24 14:22 -0400
    Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-24 21:46 +0100
      Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-24 17:09 -0400
        Re: How long should a dd take "Carlos E.R." <robin_listas@es.invalid> - 2020-03-25 01:20 +0100
          Re: How long should a dd take Jean-David Beyer <jeandavid8@verizon.net> - 2020-03-24 22:06 -0400
      Re: How long should a dd take Robert Heller <heller@deepsoft.com> - 2020-03-24 16:38 -0500

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