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Optimum HDD temperature
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-a...0070297085.php - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#2
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Optimum HDD temperature
Franc Zabkar kenjka:
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/techl...s/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/techlib.nsf/techdocs/98EE13311A54CAC886257171005E0F16/$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, http://inovator.blog.hr http://calypso-innovations.blogspot.com/ |
#4
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Optimum HDD temperature
Franc Zabkar kenjka:
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...eck.060228.pdf -- Na stolu se prekjucer zbijen penzionero kolje. By runf Damir Lukic, http://inovator.blog.hr http://calypso-innovations.blogspot.com/ |
#5
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Optimum HDD temperature
On Wed, 21 Jan 2009 21:18:03 +0000 (UTC),
lid put finger to keyboard and composed: Franc Zabkar kenjka: 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...eck.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 -- Please remove one 'i' from my address when replying by email. |
#6
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Optimum HDD temperature
On Thu, 22 Jan 2009 10:08:58 +1100, Franc Zabkar
put finger to keyboard and composed: 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 -- Please remove one 'i' from my address when replying by email. |
#7
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Optimum HDD temperature
Franc Zabkar kenjka:
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. 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, http://inovator.blog.hr http://calypso-innovations.blogspot.com/ |
#8
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Optimum HDD temperature
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#9
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Optimum HDD temperature
Franc Zabkar kenjka:
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. 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... 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. 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, http://inovator.blog.hr http://calypso-innovations.blogspot.com/ |
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