Optimum HDD temperature

[Franc Zabkar]

After unpacking the ISO that Seagate recently provided to address a
"bricking" bug in its Barracuda 7200.11 drives, I found the following
SD1A firmware image:

http://www.users.on.net/~fzabkar/SD1AMOOS.LOD

Peeking inside the code, I found some interesting text strings in two
sections :

Invalid Preheat
Preheat Time
Heater DAC
WrPreHt
WrHt
RdHt

Delta Clearance Due To Temperature
Read Fly Height
Write Fly Height
Write heat
Read heat
Read Fly Height = %f
Write Fly Height = %f
Preheat = %x, Write heat = %x, Read heat = %x

It seems to me that HDDs must incorporate a heater to bring the HDA up
to an optimum temperature so that the R/W flying height is at an
optimum level.

This observation is supported somewhat by a Samsung patent whose
inventors claim that "flying height drops significantly in humid
conditions" and that this can be remedied "by increasing the
temperature of the air flowing between a slider's air bearing surface
and the rotating disk surface it accesses".

Method and Apparatus Reducing Flying Height Drop in a Hard Disk Drive
Under Humid Conditions:
http://tinyurl.com/4s5brl
http://www.freshpatents.com/Method-...umid-conditions-dt20071227ptan20070297085.php

- Franc Zabkar

 

[calypso]

Invalid Preheat
Preheat Time
Heater DAC
WrPreHt
WrHt
RdHt

Delta Clearance Due To Temperature
Read Fly Height
Write Fly Height
Write heat
Read heat
Read Fly Height = %f
Write Fly Height = %f
Preheat = %x, Write heat = %x, Read heat = %x

It seems to me that HDDs must incorporate a heater to bring the HDA up
to an optimum temperature so that the R/W flying height is at an
optimum level.

http://www.hitachigst.com/tech/techlib.nsf/productfamilies/White_Papers

TFC - Thermal Fly-height Control, it's in use for a few years... Used to
control head height above the platters...

http://www.hitachigst.com/tech/tech...257171005E0F16/$file/TFC_whitepaper041807.pdf

This observation is supported somewhat by a Samsung patent whose
inventors claim that "flying height drops significantly in humid
conditions" and that this can be remedied "by increasing the
temperature of the air flowing between a slider's air bearing surface
and the rotating disk surface it accesses".

Flying height is related to the air humidity, because when platters turn,
then air cushion is 'created' on which heads are 'sitting'... TFC is used to
control the optimum level of the head height above platters...

Hope this helps...


--
Kamena pipa u auli PMF-a (matematika) divovski krekeru
komponiru za pet minuta ? By runf

Damir Lukic, calypso@_MAKNIOVO_fly.srk.fer.hr
http://inovator.blog.hr
http://calypso-innovations.blogspot.com/

 

[Franc Zabkar]

Franc Zabkar <[email protected]> kenjka:

http://www.hitachigst.com/tech/techlib.nsf/productfamilies/White_Papers

TFC - Thermal Fly-height Control, it's in use for a few years... Used to
control head height above the platters...

http://www.hitachigst.com/tech/tech...257171005E0F16/$file/TFC_whitepaper041807.pdf


Flying height is related to the air humidity, because when platters turn,
then air cushion is 'created' on which heads are 'sitting'... TFC is used to
control the optimum level of the head height above platters...

Hope this helps...

Yes, many thanks, it helped a lot. AIUI, there are two competing
thermal effects. On the one hand, higher ambient temperatures cause
the slider to fly higher above the platter, but on the other hand an
increased temperature causes the R/W head elements to swell and fly
closer to the disc. IIUC, TFC dynamically adjusts the flying height by
means of a uP controlled heating element embedded within the R/W head.
I'm surprised that the self heating effects of write current are so
significant, and that the heater doesn't have a significant thermal
lag, even for such a small mass.

The bottom line seems to be that there is an optimum operating
temperature for the HDD. This suggests that aggressive HDD cooling may
not be as desirable as we have been led to believe.

- Franc Zabkar

 

[calypso]

Yes, many thanks, it helped a lot. AIUI, there are two competing
thermal effects. On the one hand, higher ambient temperatures cause
the slider to fly higher above the platter, but on the other hand an
increased temperature causes the R/W head elements to swell and fly
closer to the disc. IIUC, TFC dynamically adjusts the flying height by
means of a uP controlled heating element embedded within the R/W head.
I'm surprised that the self heating effects of write current are so
significant, and that the heater doesn't have a significant thermal
lag, even for such a small mass.

The bottom line seems to be that there is an optimum operating
temperature for the HDD. This suggests that aggressive HDD cooling may
not be as desirable as we have been led to believe.

Don't forget the FDB bearings... Optimum temperature for their operation is
abour 35degC (don't know how many F)... Problem is related to the density of
the fluid in the bearings... When temperature is low, fluid is denser, and
more current (for the FDB step motor) is needed, so power consumption is
higher than optimal... When temperature is too high, it's again a problem,
because fluid looses it's viscosity...

There are a lot of temperature related stuff inside a HDD...

I've had some presentation from Maxtor laboratories...

http://www.thic.org/pdf/Feb06/maxtor.eschreck.060228.pdf


--
Na stolu se prekjucer zbijen penzionero kolje. By runf

Damir Lukic, calypso@_MAKNIOVO_fly.srk.fer.hr
http://inovator.blog.hr
http://calypso-innovations.blogspot.com/

 

[Franc Zabkar]

Franc Zabkar <[email protected]> kenjka:

Don't forget the FDB bearings... Optimum temperature for their operation is
abour 35degC (don't know how many F)... Problem is related to the density of
the fluid in the bearings... When temperature is low, fluid is denser, and
more current (for the FDB step motor) is needed, so power consumption is
higher than optimal... When temperature is too high, it's again a problem,
because fluid looses it's viscosity...

There are a lot of temperature related stuff inside a HDD...

I've had some presentation from Maxtor laboratories...

http://www.thic.org/pdf/Feb06/maxtor.eschreck.060228.pdf

I notice that there is an IBM graph on page 36 which suggests that
reliability improves at case temperatures below the recommended
temperature. This begs the question, why does the manufacturer not
recommend a lower temperature?

This is IBM's document:
http://www.hc.kz/pdf/drivetemp.pdf

Fig 2 on page 3 shows a significant improvement in reliability at
temperatures of 15 degC below the recommended temperature. Presumably
this is well below the 35 degC you have suggested as the optimum
temperature for FDB bearings.

- Franc Zabkar

 

[Franc Zabkar]

This is IBM's document:
http://www.hc.kz/pdf/drivetemp.pdf

Fig 2 on page 3 shows a significant improvement in reliability at
temperatures of 15 degC below the recommended temperature. Presumably
this is well below the 35 degC you have suggested as the optimum
temperature for FDB bearings.

I just realised that IBM's paper is dated 10/97. Maybe different
factors/considerations apply to today's drives.

- Franc Zabkar

 

[calypso]

I just realised that IBM's paper is dated 10/97. Maybe different
factors/considerations apply to today's drives.

That was the first thing I was looking for...

Back then, ball bearing step motors were used... Fluid dynamic bearings came
later...

But, thanks for the PDF... Do you have any in-depth information regarding
SMART technology? How it works, what it looks for, etc...


BTW., I sent you an email, don't know if you've got it...

--
U ormaru se za svaku Novu Godinu bodljikav Zidovo kolje.
By runf

Damir Lukic, calypso@_MAKNIOVO_fly.srk.fer.hr
http://inovator.blog.hr
http://calypso-innovations.blogspot.com/

 

[Franc Zabkar]

Do you have any in-depth information regarding
SMART technology?

No, when it comes to HDD technology, I'm on the outside looking in.
I'm just curious, that's all.

How it works, what it looks for, etc...

I wish Seagate and others would come clean on how they implement the
SMART specs. AFAICS, Seagate for one must be hurting whenever anyone
queries their extremely high raw numbers for Seek Error Rate and Read
Error Rate, for example. I wonder how many people have RMA'ed
perfectly good drives based on these data.

BTW., I sent you an email, don't know if you've got it...

Yes, I got it.

- Franc Zabkar

 

[calypso]

No, when it comes to HDD technology, I'm on the outside looking in.
I'm just curious, that's all.

Well, I fried one drive today... Tried to overvolt it's motor to 24V...
The problem was with electronics, I set it up on 7V, which was too much...
))))))))

Anyway, will try again when I got some other dead drives... Just want to
know if the motor can spin faster and if it can initialize a drive at those
speeds...

I wish Seagate and others would come clean on how they implement the
SMART specs. AFAICS, Seagate for one must be hurting whenever anyone
queries their extremely high raw numbers for Seek Error Rate and Read
Error Rate, for example. I wonder how many people have RMA'ed
perfectly good drives based on these data.

Well, I have just a few Seagate drives (36GB SCSI, 80GB ATA, 100GB SATA
2.5"), and I never check SMART... It comes at the boot sequence, motherboard
notifies me that the drive will die soon, so I can backup data and change
it...

You seem to know much about Seagate drives...

--
Pudinga gleda na jedrilici lijep kondomo sere danima ?
By runf

Damir Lukic, calypso@_MAKNIOVO_fly.srk.fer.hr
http://inovator.blog.hr
http://calypso-innovations.blogspot.com/