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Re: `pv` rates (was: burn iso to usb)

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On Mon 02 Aug 2021 at 13:26:19 (-0400), Stefan Monnier wrote:
> Anssi Saari [2021-08-02 19:04:59] wrote:
> > David Wright <deblis@lionunicorn.co.uk> writes:
> >> On Mon 02 Aug 2021 at 16:14:15 (+0300), Anssi Saari wrote:
> >>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
> >>> >>> > cp /path/to/file.iso /dev/sdX
> >>> >>> dd if=whatever.iso of=/dev/sdX  
> >>> >> It's up to taste.
> >>> >
> >>> > Not at all.  The only right answer is:
> >>> >
> >>> >     pv -parIe </path/to/file.iso >/dev/sdX
> >>> 
> >>> Actually I'm not sure how good it is to have both -a and -r, pv doesn't
> >>> really show which rate counter is which...
> >>
> >> No need: the rate is far more variable than its average, as time passes.
> >
> > I guess it depends. Before that comment I tried it on an old USB
> > stick. Read speed was pretty much constant if low. So I think it was the
> > left rate counter that showed current rate but wouldn't bet on it.
> 
> [ I'm glad my silly intervention brings up a more constructive
>   discussion ;-)  ]
> 
> If they're both pretty much constant, they're presumably both pretty
> much equal, so it doesn't matter which is which ;-)
> 
> But indeed, it's not always the case.  I'm right now using `pv` to read
> data off of a broken drive (a 2TB 2½" drive which apparently has
> problems seeking, resulting in a transfer rate of about 45kB/s), and
> it's currently showing me 45.0KiB/s and 70.6KiB/s both of which are
> quite stable.

Writing "quite stable" cloaks the information nicely. The average can
never move away from the rate: a change in the least significant digit
gives the game away.

> If it weren't for the first sometimes changing to
> 44.xKiB/s it'd be hard to know which is which (IIUC the average is
> higher because occasionally the drive gives a more reasonable transfer
> rate than that measly 45kB/s).

So now we're left wondering how you came by this situation. Perhaps
you slumped onto the Return key, then woke up after a few minutes,
having missed the initial burst that gave rise to the average being
more than 50% faster than the current rate.

Cheers,
David.

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burn iso to usb Gunnar Gervin <dofeelok@gmail.com> - 2021-07-31 14:10 +0200
  Re: burn iso to usb Nicolas George <george@nsup.org> - 2021-07-31 14:10 +0200
    Re: burn iso to usb <tomas@tuxteam.de> - 2021-07-31 14:40 +0200
    Re: burn iso to usb Hans <hans.ullrich@loop.de> - 2021-07-31 18:50 +0200
      Re: burn iso to usb Nicolas George <george@nsup.org> - 2021-07-31 18:50 +0200
      Re: burn iso to usb Greg Wooledge <greg@wooledge.org> - 2021-07-31 19:40 +0200
        Re: burn iso to usb <tomas@tuxteam.de> - 2021-07-31 20:00 +0200
      Re: burn iso to usb <tomas@tuxteam.de> - 2021-07-31 19:40 +0200
        Re: burn iso to usb Stefan Monnier <monnier@iro.umontreal.ca> - 2021-07-31 20:40 +0200
          Re: burn iso to usb <tomas@tuxteam.de> - 2021-07-31 20:50 +0200
            Re: burn iso to usb "Thomas Schmitt" <scdbackup@gmx.net> - 2021-07-31 21:10 +0200
          Re: burn iso to usb Anssi Saari <as@sci.fi> - 2021-08-02 15:20 +0200
            Re: burn iso to usb David Wright <deblis@lionunicorn.co.uk> - 2021-08-02 17:50 +0200
              Re: burn iso to usb Anssi Saari <as@sci.fi> - 2021-08-02 18:10 +0200
                `pv` rates (was: burn iso to usb) Stefan Monnier <monnier@iro.umontreal.ca> - 2021-08-02 19:30 +0200
                Re: `pv` rates (was: burn iso to usb) David Wright <deblis@lionunicorn.co.uk> - 2021-08-02 21:00 +0200
                Re: `pv` rates Stefan Monnier <monnier@iro.umontreal.ca> - 2021-08-02 21:20 +0200
                Re: `pv` rates David Wright <deblis@lionunicorn.co.uk> - 2021-08-04 18:00 +0200
                [OFFTOPIC] Fun with pv and broken drive (was: `pv` rates) Stefan Monnier <monnier@iro.umontreal.ca> - 2021-08-04 19:30 +0200
            Re: burn iso to usb Gunnar Gervin <dofeelok@gmail.com> - 2021-08-02 21:10 +0200
              Re: burn iso to usb Greg Wooledge <greg@wooledge.org> - 2021-08-02 21:50 +0200
                Re: burn iso to usb <tomas@tuxteam.de> - 2021-08-02 22:00 +0200
                Re: burn iso to usb Nicolas George <george@nsup.org> - 2021-08-02 22:00 +0200
                Re: burn iso to usb Gunnar Gervin <dofeelok@gmail.com> - 2021-08-03 14:30 +0200
                Re: burn iso to usb Gunnar Gervin <dofeelok@gmail.com> - 2021-08-03 14:40 +0200
        Re: burn iso to usb Robbi Nespu <robbinespu@gmail.com> - 2021-08-02 12:30 +0200
    Re: burn iso to usb Gunnar Gervin <dofeelok@gmail.com> - 2021-08-01 21:10 +0200

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