Previously Franc Zabkar <fzabkar@iinternode.on.net> wrote:
Ah. That would be a different type of dynamics, that, while having
some fluid properties, is not fluid dynamics.

I am just saying that very likely all HDDs in the study were
running with similar humidity, and therefore humidity will
not be a factor examined.

Arno

On 21 Apr 2008 23:04:10 GMT, Arno Wagner <me@privacy.net> put finger
to keyboard and composed:

http://en.wikipedia.org/wiki/Fluid_dynamics

"Fluid dynamics is the sub-discipline of fluid mechanics dealing with
fluid flow: fluids (liquids and gases) in motion. It has several
subdisciplines itself, including aerodynamics (the study of gases in
motion) ... Fluid dynamics has a wide range of applications, including
calculating forces and moments on aircraft ..."

.... and on flying disc heads?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote in news:jq6v04pghj6ilcu188g2enl14opavt48j0@4ax.com
Gee, there's a big surprise.

Personal experience, no less.

Right, and it was you 'personally' that held the heads off track.

One reason could be that this is an average and the increase of the ave-
rage is caused by just some writes having to wait another full rev due to
the servo system deciding it's not certain that it is on the correct track
due to the sector being near but not enough track marks on the track,
to have read (just) one, before the sector arrives.
On a read the drive can read the sector and confirm the track number
afterwards and let it go through (or not) depending on the outcome. On
a write that's not possible as that's destructive and it doesn't want the
wrong sector overwritten so it lets the opportunity pass and do another rev.

Nothing to do with the heads "having settled" and poor
reads that make or don't make it through error correction.

Close, but that's not what he said.

Previously Franc Zabkar <fzabkar@iinternode.on.net> wrote:
Oh, ok. Different usage in my physics course (which was in
german), it seems.

Arno

Arno Wagner wrote in news:677f78F2nlmkvU1@mid.individual.net
And, as we all know, german physics are different from
the rest of the world's physics. That explains it all.
Thanks babblebot, you nailed it, once again.
What should we do without you, eh. Imagine that.

On 17 Apr 2008 20:56:34 GMT, Arno Wagner <me@privacy.net> put finger
to keyboard and composed:

I've been searching for references to support your statement but I
haven't had any luck. I know from personal experience that older
drives could be commanded to seek with a positive or negative track
offset. Positioning the head slightly off-track and attempting a read
was commonly done during low level formatting to test the integrity of
the data surface. Any track that failed would be taken out of service
and replaced with a spare. Servo offsets could also be used when
recovering data from marginal sectors.

I notice that some Seagate product manuals specify a lower number for
average seek time during reads as opposed to writes (8.5ms versus
10ms). Track-to-track seeks are also lower (0.8ms versus 1.0ms). I
don't know whether this reflects the operation of the drive's read
ahead cache or whether it supports your claim regarding a "preemptive"
read strategy.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Previously Franc Zabkar <fzabkar@iinternode.on.net> wrote:
Actually I do not have a good reference myself. It is something
that accumulated when looking into modern HDD technology and
the possibilities of recovering overwritten data. Supporting
data is that for some intermediate HDD generations reads
were faster than writes by a notable margin. I do not remember
exactly whether I found an explicit statement about this behaviour,
or whether it is my conclusion from accumulayed facts. So, strictly
speaking, this may only be a hypothesis, but is is a good one.

Ah, so this is still going on.

Caches/buffers are not involved here. Otherwise they would
certainly also include them for writing, and write-buffers
can hav a lot more impact than read-ahead.

Arno

On 24 Apr 2008 06:42:53 GMT, Arno Wagner <me@privacy.net> put finger
to keyboard and composed:

Yes, that makes sense. It seems, then, that your preemptive read
hypothesis is plausible.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote in news:0il0141ha4hojccg9r0sj6lvsujtget8vo@4ax.com
Yes it is, just not what he thinks it is. And it's your naming, not his.

Arno Wagner wrote in news:67aofdF2o6q6kU1@mid.individual.net
Of course not. You are Babblebot, you don't need one.

No, it's nonsense.

Like the physics changed over time, you babblebot moron.

Actually, it would reduce the seektime to zero, zip, nada.