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Re: Question: SSD speed

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On Wed, Oct 07, 2020 at 12:48:09PM +0200, Sven Hartge wrote:
>Jeremy Nicoll <jn.ml.dbn.25@letterboxes.org> wrote:
>> On Wed, 7 Oct 2020, at 09:39, Hans wrote:
>
>>> I have a little question. Smartctl is telling me, that my ssd drive
>>> is 6Gb/sec capable, but the actual speed is only 1,5GB/sec.
>
>> If your SATA (presumably) connection from the machine to the SSD is a
>> 6 Gbps one, the maximum data transfer speed in bytes across that
>> connection would be one eighth of that (as there's 8 bits per byte),
>> so about 760 MBps.
>
>> That's about half of your "1,5GBps".  That makes me wonder if your SSD
>> uses two SATA channels at once - is that even possible?
>
>Only with SAS drives. And usually only for redudancy and not for
>concurrency.
>
>I question the benchmark Hans did.
>
>Something tells me he either used "hdparm -tT", which is known to
>misrepresent the speeds on modern drives, or wrote too little data so he
>was benchmarking the Kernel cache and not the drive.

I'd assume it's confusion between bits and bytes. For clarity, *never* 
use B or b, just write out bit or byte because some people put attach 
much more significance to the case of that letter than others--making it 
basically useless for communication. As others have already pointed out, 
there's probably a mismatch between SATA versions causing a SATA III 
6Gbit/s device to negotiate down to SATA I 1.5Gbit/s. It's likely that 
the only solution is to replace the SATA controller. (Unlikely to be 
feasible in a portable device.) There is a small chance that it could be 
a bad cable and that replacing the cable would help.

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Question: SSD speed Hans <hans.ullrich@loop.de> - 2020-10-07 10:50 +0200
  Re: Question: SSD speed Georgi Naplatanov <gosho@oles.biz> - 2020-10-07 11:40 +0200
  Re: Question: SSD speed Steve McIntyre <steve@einval.com> - 2020-10-07 12:00 +0200
  Re: Question: SSD speed "Jeremy Nicoll" <jn.ml.dbn.25@letterboxes.org> - 2020-10-07 12:00 +0200
    Re: Question: SSD speed Sven Hartge <sven@svenhartge.de> - 2020-10-07 12:50 +0200
      Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-07 15:10 +0200
        Re: Question: SSD speed Andrei POPESCU <andreimpopescu@gmail.com> - 2020-10-08 11:00 +0200
          Re: Question: SSD speed "Thomas Schmitt" <scdbackup@gmx.net> - 2020-10-08 12:00 +0200
            [SOLVED] Re: Question: SSD speed Hans <hans.ullrich@loop.de> - 2020-10-08 12:20 +0200
            Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-08 15:20 +0200
              Re: Question: SSD speed "Thomas Schmitt" <scdbackup@gmx.net> - 2020-10-08 16:00 +0200
                Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-08 16:20 +0200
                Re: Question: SSD speed Stefan Monnier <monnier@iro.umontreal.ca> - 2020-10-08 17:40 +0200
                Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-08 17:50 +0200
                Re: Question: SSD speed Stefan Monnier <monnier@iro.umontreal.ca> - 2020-10-08 18:00 +0200
              Re: Question: SSD speed Leslie Rhorer <lesrhorer@att.net> - 2020-10-08 20:30 +0200
                Re: Question: SSD speed Dan Ritter <dsr@randomstring.org> - 2020-10-08 20:40 +0200
                Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-08 21:20 +0200
                Re: Question: SSD speed Leslie Rhorer <lesrhorer@att.net> - 2020-10-09 02:00 +0200
                Re: Question: SSD speed Michael Stone <mstone@debian.org> - 2020-10-09 02:20 +0200
                Re: Question: SSD speed Leslie Rhorer <lesrhorer@att.net> - 2020-10-09 02:40 +0200
                Re: Question: SSD speed Stefan Monnier <monnier@iro.umontreal.ca> - 2020-10-09 00:20 +0200
                Re: Question: SSD speed Leslie Rhorer <lesrhorer@att.net> - 2020-10-09 02:20 +0200
                Re: Question: SSD speed Stefan Monnier <monnier@iro.umontreal.ca> - 2020-10-09 15:50 +0200
    Re: Question: SSD speed Alberto Sentieri <22t@tripolho.com> - 2020-10-07 13:30 +0200
      Re: Question: SSD speed "Jeremy Nicoll" <jn.ml.dbn.25@letterboxes.org> - 2020-10-07 14:50 +0200
        Re: Question: SSD speed Andrei POPESCU <andreimpopescu@gmail.com> - 2020-10-08 10:50 +0200
    Re: Question: SSD speed Hans <hans.ullrich@loop.de> - 2020-10-07 18:50 +0200
      Re: Question: SSD speed "Jeremy Nicoll" <jn.ml.dbn.25@letterboxes.org> - 2020-10-07 18:50 +0200
      Re: Question: SSD speed Andy Smith <andy@strugglers.net> - 2020-10-07 19:50 +0200
        [SOLVED] Re: Question: SSD speed Hans <hans.ullrich@loop.de> - 2020-10-07 20:00 +0200
        [SOLVED] Re: Question: SSD speed Hans <hans.ullrich@loop.de> - 2020-10-08 09:10 +0200
  Re: Question: SSD speed Andrei POPESCU <andreimpopescu@gmail.com> - 2020-10-08 11:00 +0200

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