From: Michael Stone
Subject: Re: SCSI vs SATA
Date: ,
Msg-id: 20070406181912.GF4374@mathom.us
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In response to: Re: SCSI vs SATA  (Ron)
Responses: Re: SCSI vs SATA  (Ron)
List: pgsql-performance

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SCSI vs SATA  ("", )
 Re: SCSI vs SATA  (Ron, )
  Re: SCSI vs SATA  (Ron, )
   Re: SCSI vs SATA  (Geoff Tolley, )
    Re: SCSI vs SATA  (, )
     Re: SCSI vs SATA  ("Peter Kovacs", )
      Re: SCSI vs SATA  (Andreas Kostyrka, )
       Re: SCSI vs SATA  (Alvaro Herrera, )
        Re: SCSI vs SATA  ("Peter Kovacs", )
         Re: SCSI vs SATA  (Alvaro Herrera, )
          Re: SCSI vs SATA  (Andreas Kostyrka, )
         Re: SCSI vs SATA  (, )
       Re: SCSI vs SATA  (Rod Taylor, )
     Re: SCSI vs SATA  (Geoff Tolley, )
    Re: SCSI vs SATA  ("", )
     Re: SCSI vs SATA  ("Joshua D. Drake", )
      Re: SCSI vs SATA  (Stefan Kaltenbrunner, )
       Re: SCSI vs SATA  ("Joshua D. Drake", )
        Re: SCSI vs SATA  (Stefan Kaltenbrunner, )
         Can't drop tablespace or user after disk gone  ("Craig A. James", )
          Re: Can't drop tablespace or user after disk gone  (Tom Lane, )
       Re: SCSI vs SATA  ("James Mansion", )
      Re: SCSI vs SATA  (Andreas Kostyrka, )
       Re: SCSI vs SATA  ("Joshua D. Drake", )
        Re: SCSI vs SATA  (, )
         Re: SCSI vs SATA  (Geoff Tolley, )
         Re: SCSI vs SATA  (Bruce Momjian, )
          Re: SCSI vs SATA  ("Joshua D. Drake", )
           Re: SCSI vs SATA  (Bruce Momjian, )
            Re: SCSI vs SATA  ("James Mansion", )
             Re: SCSI vs SATA  (Tom Lane, )
              Re: SCSI vs SATA  (Scott Marlowe, )
               Re: SCSI vs SATA  (Ron, )
                Re: SCSI vs SATA  (, )
                 Re: SCSI vs SATA  (Tom Lane, )
                  Re: SCSI vs SATA  (Greg Smith, )
                   Re: SCSI vs SATA  (Tom Lane, )
                    Re: SCSI vs SATA  (Geoffrey, )
                  Re: SCSI vs SATA  (Michael Stone, )
                   Re: SCSI vs SATA  (Geoffrey, )
               Re: SCSI vs SATA  ("James Mansion", )
                Re: SCSI vs SATA  (Scott Marlowe, )
                 Re: SCSI vs SATA  (, )
                  Re: SCSI vs SATA  (Ron, )
                   Re: SCSI vs SATA  (, )
                    Re: SCSI vs SATA  (Richard Troy, )
                    Re: SCSI vs SATA  (Ron, )
                     Re: SCSI vs SATA  (, )
                      Re: SCSI vs SATA  (Ron, )
                       Re: SCSI vs SATA  (Mark Kirkwood, )
                   Re: SCSI vs SATA  (Michael Stone, )
                    Re: SCSI vs SATA  (Ron, )
                     Re: SCSI vs SATA  (Michael Stone, )
                      Re: SCSI vs SATA  (Ron, )
                       Re: SCSI vs SATA  (Michael Stone, )
                        Re: SCSI vs SATA  (Ron, )
                         Re: SCSI vs SATA  (Michael Stone, )
                 Re: SCSI vs SATA  (Greg Smith, )
                  Re: SCSI vs SATA  (Scott Marlowe, )
                   Re: SCSI vs SATA  (Greg Smith, )
                   Re: SCSI vs SATA  (, )
                    Re: SCSI vs SATA  (Charles Sprickman, )
                     Re: SCSI vs SATA  (, )
                     Re: SCSI vs SATA  (Andreas Kostyrka, )
                   Re: SCSI vs SATA  (Bruce Momjian, )
                    Re: SCSI vs SATA  (Ron, )
                     Re: SCSI vs SATA  (, )
                      Re: SCSI vs SATA  (Ron, )
                       Re: SCSI vs SATA  (, )
                        Re: SCSI vs SATA  ("Joshua D. Drake", )
                        Re: SCSI vs SATA  (Ron, )
                       Re: SCSI vs SATA  (, )
                 Re: SCSI vs SATA  ("James Mansion", )
           Re: SCSI vs SATA  (Carlos Moreno, )
            Re: SCSI vs SATA  ("", )
             Re: SCSI vs SATA  (Arjen van der Meijden, )
             Re: SCSI vs SATA  (Heikki Linnakangas, )
             Re: SCSI vs SATA  (Ron, )
              Re: SCSI vs SATA  ("", )
               Re: SCSI vs SATA  ("Joshua D. Drake", )
               Re: SCSI vs SATA  ("Alex Deucher", )
               Re: SCSI vs SATA  (Arjen van der Meijden, )
               Re: SCSI vs SATA  (, )
     Re: SCSI vs SATA  (Geoff Tolley, )
     Re: SCSI vs SATA  (Scott Marlowe, )
      Re: SCSI vs SATA  (Jeff Frost, )
       Re: SCSI vs SATA  ("", )
 Re: SCSI vs SATA  ("Brian A. Seklecki", )
 Re: SCSI vs SATA  (Ron Mayer, )
 Re: SCSI vs SATA  (Ron, )
 Re: SCSI vs SATA  (Arjen van der Meijden, )
  Re: SCSI vs SATA  ("", )
   Re: SCSI vs SATA  (Arjen van der Meijden, )

On Fri, Apr 06, 2007 at 12:41:25PM -0400, Ron wrote:
>3.based on personal observation, case study
>reports, or random investigations rather than
>systematic scientific evaluation: anecdotal evidence.

Here you even quote the appropriate definition before ignoring it.

>In short, professional advice and opinions are
>supposed to be considerably more rigorous and
>analytical than anything "anecdotal".  The alternative is "malpractice".

In any profession where malpractice is applicable, the profession
opinion had better be backed up by research rather than anecdote. I'm
not aware of any profession held to a "malpractice" standard which is
based on personal observation and random investigation rather than
formal methods.

>studies.  I respect that.  Unfortunately the RW
>is too fast moving and too messy to wait for a
>laboratory style study to be completed before we
>are called on to make professional decisions on
>most issues we face within our work
>IME I have to serve my customers in a timely
>fashion that for the most part prohibits me from
>waiting for the perfect experiment's outcome.

Which is what distinguishes your field from a field such as engineering
or medicine, and which is why waving the term "malpractice" around is
just plain silly. And claiming to have to wait for perfection is a red
herring. Did you record the numbers of disks involved (failed &
nonfailed), the models, the environmental conditions, the poweron hours,
etc.? That's what would distinguish anecdote from systematic study.

>Agreed.  OTOH, there's not supposed to be
>anything casual, ill-considered, or low quality
>about professionals giving professional opinions within their
>fields of expertise.  Whether numbers are explicitly involved or not.

If I go to an engineer and ask him how to build a strong bridge and he
responds with something like "Well, I always use steel bridges. I've
driven by concrete bridges that were cracked and needed repairs, and I
would never use a concrete bridge for a professional purpose." he'd lose
his license.  You'd expect the engineer to use, you know, numbers and
stuff, not anecdotal observations of bridges. The professional opinion
has to do with how to apply the numbers, not fundamentals like 100 year
loads, material strength, etc.

What you're arguing is that your personal observations are a perfectly
good substitute for more rigorous study, and that's frankly ridiculous.
In an immature field personal observations may be the best data
available, but that's a weakness of the field rather than a desirable
state. 200 years ago doctors operated the same way--I'm glad they
abandoned that for a more rigorous approach. The interesting thing is,
there was quite a disruption as quite a few of the more established
doctors were really offended by the idea that their professional
opinions would be replaced by standards of care based on large scale
studies.

Mike Stone


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