[nylug-talk] Paper IT certs and disk drive fabrication differences -- WAS: Slim home server

[Chris Knadle]

On Friday 23 May 2008, Bryan J. Smith wrote:
> Chris Knadle wrote:
> > ?  No.  The specifications say 700,000 hours MTBF, 50,000
> > "contact start-stops", and nothing about how many hours per
> > day --
>
> Okay then, 14 hours/day for 700,000 hours MTBF.  ;)

   And where'd you pull that number from?  What spec?  What calculation?  All 
you've done is give me another unusuable OTTOMA number.  [Off The Top Of 
My ...]

> You're still not reading my entire post.  You're pick'n and choosing
> what you want to assume, believe or otherwise.

   I read your posts.  Fully.  You're suggesting otherwise.  That's insulting.  
If I somehow misinterpreted your words, then maybe you can correct me and 
make it more clear.

> I hope you'd pick up on this, as I've made every, detailed effort to
> explain many, many concepts.  But you keep removing the context of
> those posts.  My knowledge comes from direct product managers of
> various lines.

   What I have from you is a vague "trust me I know what I'm talking about", 
which may very well be (and I generally agree with that), but then out comes 
a number of hours/day as if it were in the spec when it's not.  Sorry, but 
that's called heresay.

   As for cutting the context -- I don't want to send all 10 Kb back every 
time I reply.  You're trying to be accurate, but you're also terribly 
verbose; far more than I'd wish to be.  So I have to try to limit responses 
so that you don't blow them up out of proportion.  :-/

> He said most of his peers are now getting their commodity 187-320GB
> platters from the same fab in Malaysia is now.  Western Digital seems
> to have the largest stake.  That's quite a change in just the last
> few years it seems.

> Chris Knadle wrote:
> > please explain where you're getting this 8 hours/day usage from.
>
> Industry standard practice.  This is technical fact.

   But that still doesn't answer the question.  Is there a place I can look 
this number up from?  That's what I need; not a statement of "it's a fact", 
because that's not fact, that's opinion.

> Commodity disk:
>   50,000 starts/stops * X hours = the MTBF rating  ;)

   Continuous use = far fewer stops.
   You knew that was coming.

> But MTBF is not considered an usable number though, and hasn't been
> for a long time.  But it is still quoted.  A better practice is the
> change of failure, assuming standard operating conditions, per 6 or
> 12 months.  It currently stands at just over 2%.  Different lots
> often vary by +/-0.6% or greater last time I checked, but I'm
> probably outta date.

   Typically the MTBF is arrived by via artificial aging, running the drive 
continously at increased environmental stresses, and a number is extrapolated 
from the artificial aging tests.  This is obvious, of course, because no 
manufacturer can wait 400,000 or 700,000 hours before starting to sell the 
drives that have MTBF specs printed on them.
   This is at least as far as I know.  But again, if that's the case, then the 
MTBF number is based on continuous use.

> With that all said ...
>
> I'm sorry to be rude, but when you actually want to discuss the
> greater points I was making, feel free to re-engage.  Until then, I
> must ignore your posts.  Again, don't mean to be rude, but I'm
> re-covering industry standard facts and practices over and over and
> over again.  You're just taking what you want out of my posts and
> making _microcosms_ out of them, _ignoring_ the context I made them
> in.
>
> Result?
>
> Nothing but a meta-discussion well outside any of my points.  ;)

   Numbers out of the air, that's what I'm objecting to.

> If that's not enough ...
>
>   "You win.  I'm wrong.  You're right."
>
> Believe what you want to believe.  I'm not the consultant I am
> because I want to believe what I want.  I'm just the consultant
> because I put things in terms of mitigating risk and avoiding legal
> issues.  That's engineering, not some arbitrary black/white
> assumption of technology.  ;)

   Look: if your opinion is that "server-grade" hard disks are more suitable 
for servers, I agree with you.  You've eloquently explained that the 
manufacturing and QA processes for some hard disks are of a higher standard 
than others, and as such they can last longer.  I'm fine with all of those 
theories.  So for the most part we agree.
   With the obvious exeptions.

   I'm dropping this now.

   -- Chris

-- 

Chris Knadle
Chris.Knadle at coredump.us