Date: Fri, 06 Apr 2007 17:02:29 -0400
From: Michael Stone <mstone+postgres@mathom.us>
Subject: Re: SCSI vs SATA
In-reply-to: <E1HZuFH-0005I9-8Z@elasmtp-mealy.atl.sa.earthlink.net>
To: Ron <rjpeace@earthlink.net>
Cc: pgsql-performance@postgresql.org
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On Fri, Apr 06, 2007 at 03:37:08PM -0400, Ron wrote:
>>>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.
>
>Ok, since you know I am an engineer that crossed a professional line 
>in terms of insult.  That finishes this conversation.

Actually, I don't know what you are. I obviously should have been more 
specific that the field I was refering to is computer systems 
integration, which isn't a licensed engineering profession in any 
jurisdiction that I'm aware of. 

>...and you know very well that the use of the term "malpractice" was 
>not in the legal sense but in the strict dictionary sense: "mal, 
>meaning bad" "practice, meaning "professional practice."

That's the literal definition or etymology; the dictionary definition 
will generally include terms like "negligence", "established rules", 
etc., implying that there is an established, objective standard. I just 
don't think that hard disk choice (or anything else about designing a 
hardware & software system) can be argued to have an established 
standard best practice. Heck, you probably can't even say "I did that 
sucessfully last year, we can just implement the same solution" because 
in this industry you probably couldn't buy the same parts (exagerrating 
only somewhat).

>>  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 power on hours, etc.? 
>>That's what would distinguish anecdote from systematic study.
>
>Yes, as a matter of fact I =do= keep such maintenance records for 
>operations centers I've been responsible for.

Great! If you presented those numbers along with some context the data 
could be assessed to form some kind of rational conclusion. But to 
remind you of what you'd offered up to the time I suggested that you 
were offering anecdotal evidence in response to a request for 
statistical evidence:

>OTOH, I've spent my career being as careful as possible to as much as 
>possible run HW within manufacturer's suggested specifications. I've 
>been chided for it over the years... ...usually by folks who "save" 
>money by buying commodity HDs for big RAID farms in NOCs or push their 
>environmental envelope or push their usage envelope or ... ...and then 
>act surprised when they have so much more down time and HW replacements 
>than I do.
>
>All I can tell you is that I've gotten to eat my holiday dinner far more 
>often than than my counterparts who push it in that fashion.

I don't know how to describe that other than as anecdotal. You seem to 
be interpreting the term "anecdotal" as pejorative rather than 
descriptive. It's not anecdotal because I question your ability or any 
other such personal factor, it's anecdotal because if your answer to the 
question is "in my professional opinion, A" and someone else says "in my 
professional opinion, !A", we really haven't gotten any hard data to 
synthesize a rational opinion. 

Mike Stone