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Guest Keatah

Why to never buy 3.5" external HDD's

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Don't you just love those WD MyBooks? Tip them over and now you need a pro-service! Great source of income.

 

Matter of fact, it is this exact type of drive that failed.

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Guest Keatah

Many WD external housings have cutouts in the housing, or in the metal mounting and interface bracket, for a small fan. They chose not to stuff it. They might have done so in some of the WorldBook "raid" series - but I don't know about the very latest iterations of that product.

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This is a published document that refers to an overheating WD MyBook

http://www.hdsentine...se_overheat.php

The temperature level is far above the highest acceptable 50 Celsius (55 Celsius for some hard disk models or maybe 60 Celsius for some very-specific models, for example industry SAS hard disks). This high temperature can seriously damage both the mechanical and electronical parts of the hard disk.

Disclaimer :-

I use the professional version of HDSentinel but a free Trial version is available.

My motive is not to push the product but to show that 60 Celsius is far too high for the WD MyBook and many other products.

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a monthly PC mag here did a survey/test about 4-5 years ago.

they stated the average HD lasted about 2 years before failure.

 

have no idea of the breakdown between internal vs external or 3.5" vs 2.5" but it was an eye-opener.

 

bottom line - BACKUPS !

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Guest Keatah

I just got off the phone with a WD (Western Digital) representative and had been discussing a 500GB MyBook disk. This is a disk that runs hot. At least the first incarnations of this model do.

 

He said very specifically that the design life of this disk is specified and engineered to be 5 years. No more. Anything after that all bets are off. Consider the disk unreliable after that.

 

Some things not in this disk's favor are:

1- 4 platters.

2- 8 heads.

3- A second stabilizing screw through the cover, makes for unstable alignment after movements of the cover and housing flexing caused by temperature swings or physical shock.

4- 66`C operating temperature

5- Enclosure with no fan.

6- 1st generation model of this capacity level.

7- Metal shield or blanket (mounting bracket) that covers the disk further restricting airflow.

8- Large swaths of tape to hold the connectors in place. While that is good practice, it impedes airflow.

 

While this is "yesterday's capacity", 500GB, in a large 3.5 form factor - it's ready for the scrap heap (functioning or not). It represents a philosophy of making a product at the cheapest possible point. The addition of a $2.00 fan would add years of life to this drive, as would increasing the thickness of the top cover by fractions of a mil.

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i thought HD's were measured with something like 100,000 hours MTBF rating.

i know the MTBF ranking system is, at worst, completely wrong and at best, a pie-in-the-sky guess-timate extrapolated from a few hours laboratory tests but still, for a Rep to come out and openingly admit a 5 year - no more - life span seems a bit alarming.

 

so, did he or you Keatah have any evidence that the notebook drives actually do survive longer in the field?

i would have assumed that the same Thailand factory made both sorts, using the same metals, coils, air-flows etc.

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Guest Keatah

Notebook drives put into a desktop drive's environment - the 2.5" wins every time. My own testing shows this.

 

Yep. The same factory makes 2.5 and 3.5 - but the 2.5 disks are machined better, the moving parts' surfaces are smoother. They have to be, otherwise the disk wouldn't function very long.

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He said very specifically that the design life of this disk is specified and engineered to be 5 years. No more. Anything after that all bets are off.

Design Life and Actual Life can be different.

 

Five metres from my home is a public footpath, under which is a nice new yellow plastic pipe that supplies gas for the entire housing estate.

The estate was built about 30 years ago and instead of using cast iron pipes that were inclined to fracture,

they used the latest and best and safest which was ductile iron pipes.

 

Some time ago houses exploded (but not in my back yard) and it was discovered that these iron pipes were subject to corrosion in some soils,

and the actual life could be far less than the predicted design life.

That gas could leak and travel under ground for perhaps 50 metres before surfacing into a house.

About 10 years ago there was a new decree (probably by Health and Safety Executive)

that any such pipe had to be replaced by the latest and best plastic pipe.

 

Two years ago was the first time I knew of the danger when I asked the man outside my house why he was replacing the metal gas pipe with plastic,

and he showed me a 10 inch long "trophy" of 3 inch diameter pipe that he had taken from on old pipe in the next village.

Five metres from my house was a 12 inch diameter that carried enough gas to barbecue all the homes in our road.

 

The new plastic pipe has a good long design life

That does not make me comfortable :(

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Guest Keatah

i thought HD's were measured with something like 100,000 hours MTBF rating.

i know the MTBF ranking system is, at worst, completely wrong and at best, a pie-in-the-sky guess-timate extrapolated from a few hours laboratory tests but still, for a Rep to come out and openingly admit a 5 year - no more - life span seems a bit alarming.

 

Me too. I did double-take when discussing it with him on the phone. Well.. WD got wind of my complaint through another channel and said they'd be calling me next week. Perhaps they want to see the disk back in the lab for analysis. Or perhaps they want to offer me a replacement, which isn't going to shut me up or change the fact that hot disks in unventilated enclosures are risks to data loss.

 

100,000 MTBF comes out to be 11 years continuous use. But there's a lot of specifics involved in testing HDD. Continuous use.. Does that mean daily power cycling? Power on for 11 years non-stop? How much inner-outer-inner track access? And time between track access? What environmental conditions? How many reads? Writes?

 

All that.. all that can make for some pretty varied duty cycles. Which reminds me, one of the key aspects of 2.5" durability is the smaller mass of the platters. The platter size reduction and corresponding bearing size reduction in going from 3.5 to 2.5 is largely disproportionate. The bearings seem "extra beefy" in a 2.5 disk when you consider their size in proportion to the platters. It's also important to remember that the platters are necessarily thicker in 3.5 disks. Extra dead mass that does nothing except to provide rigidity.

 

Ever notice how a 2.5 gets up to speed so much faster than a 3.5? Thanks to a low rotational mass and oversize bearing, these cycles produce little or no wear!

 

But in 3.5 you got all sorts of uneven torque lasting many seconds, perhaps 10 seconds in a green disk.

 

2.5 disks are made to experience many more cycles of head parkings. Many models are tested to the low millions. With the minimum spec (today) being 600,000. You can thank power-savings' spindowns for that level of required engineering!

 

Regarding design life. The first MER spacecraft (mars rovers), were made to last something like six months, and here we are, today, with one of them going on 9 years old. So much for design life predictions. Both would be working, but JPL got stupid and drove one into quicksand.

 

--------------------------------------------

 

For those of you wondering exactly how to use the S.M.A.R.T. data, consider this:

 

Disk drives are electro-mechanical devices. They are subject to wear and tear over time. You've got solid-state electron migration in the semiconductor circuits, bearing fluid dry-outs, surface-to-surface wear in bearings, head focus and sensitivity. Tolerances and shapes of metal that don't exactly return to their original dimensions after extended cycling. All that and more.

 

With age, a disk is able use closed-loop sensors to compensate for all these things. And when these things get out of hand a SMART error can happen. A head may not settle into position fast enough, therefore requiring extra gain to manhandle it. Extra power, extra heat, extra time. If the time takes too long, the disk's firmware considers it a slow sector and does a remap operation. This shows as a re-allocated sector. One or two isolated instances mean nothing. But a continual steady non-linear increase over a short amount time spells TROUBLE.

 

 

The point being, as the disk fights itself, the SMART errors increase - until poof!! The whole works blows up. Use SMART holistically and big-picture style.

 

My laptop has a good number of SPIN RETRY COUNTS going, but the disk is not bad. This comes from trying to power up with a dead battery, or killing the power while the disk is spinning up from sleep mode. Pulling the battery during disk operations.. Crap like that. There are also two reallocated sectors. Probably resulting from the same abuse or when I got mad and bashed it upside the head, no doubt.

 

-----------------------------------------

 

One more thing, if you want a high-quality 3.5 disk, spend the extra $100 and get an enterprise-class disk. These *are* top-quality units.

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I guess a 2.5" disk is designed with shock resistance to withstand a laptop being bounced around in the boot of a car,

and has no trouble surviving in an external enclosure that suffers nothing worse than sitting a a desk that gets nudged with a vacuum cleaner.

A 3.5" disk is designed for a static Tower computer - no safety margin there.

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Guest Keatah

I've dropped several 2.5" disks while in operation, some fell off the cable and thus parked their heads before they hit the ground. I've also pounded on my lappy but good, and it still works. But there is a limit to 2.5" durability.

 

SSD's are leaps and bounds ahead in this category. We bolted 3 top-tier mfgs' SSD to a jack hammer casing, and the connector failed by working itself loose before anything else did. Using silicone adhesive to hold it together and reran the test and this time it continued working for quite some time. We got bored.

 

Going further I tested another one, but this time an mSATA-style disk. We did the extreme test and put it right on the chisel tool. It continued working for a number of minutes but failed from cracked solder. We built a minimal mounting jig with rubber grommets and rings. This time the disk continued working for much longer. We got bored and stopped the test. Absolutely thrilling.

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