Single density disks failing at a faster rate than double density?

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I've noticed recently that my SD disks are failing at a much higher rate than DD. However, on average, my SD disks are older than my DS disks.

Is there something unique about using SD disks on the Apple II that results in greater failure rate, or is it more likely just that the disks are a couple of years older? They are all stored under the same conditions.

My failure rate for DD disks has risen to about 1.5%/yr, while SD are at 19%. (By no means a rigorous, scientific test, but I do keep basic stats.)

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Re: Single density disks failing at a faster rate than ...

Out of about 3800 floppies which were written either by the factory or my Disk II drive, I'
ve got 9 failures. And those failures are single sectors, perhaps 3 or 4 sectors per disk at most, and the sectors are near each other.

The mix is about 20% factory and 80% my drive. I've not noticed any difference based on density. But I believe most of my disks are SS/DD.

I'm quite pleased with the longevity, I've had these disks since the late 70's and early 80's!

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Re: Single density disks failing at a faster rate than ...

Hello,

it´s probably usefull to know that in former days the companies performed a kind of sieve during production of the disks....

at the end of the factory road the disks were tested automatically several times....
those with no mistakes at both sides went to packing for double sided double density ( DS DD )... Quality A
those with no mistakes at one side went to packing for single sided double density ( SS DD ) ... Quality B
those with less quality but average acceptable coating on both sides went for the packages of single density double sided ( DS SD ) Quality C
and those that passed at least the requested average at one side went to the packages single sided single density ( SS SD ) Quality D
and the rest at the sieve that did not pass quality control ended in the trash....

and some factories did not sieve for the sides but only for Quality A or Quality C ... thats the reason that often also disks have been sold as single sided single density but had a coating on both sides because if the quality not passed A but C they were sold for Quality D.... ( the reason for this was saving money in quality control at the factory )

thats the one side of the coin...
- but there is another side of the coin too...
at single sided drives like the APPLE II
the single sided drives have in nealy each case at the oposite side a lever with soft material like a sponge that presses the disk down to the read/write head to make sure the disk keeps close to the head ...
that rubs along the oposite side and though its made from soft material the permanent use scratches off with age some thin part of the coating.... and after long period it might damage the backside of the disk...
but in former days the disk were that expensive that users, when they discovered that the disks often had a coating at both sides, punched in with a disk notcher a second notch and used both sides....
pictures of that can be viewed at:
http://www.harrowalsh.de/Elektronik/APPLEBOX/appleboxdiskiipage1.htm

but of course if the backside of the disk are used too in the singlesided drives, that "sponge" scratches along the surface of the certified side of the disk.... and that removes very slowly but sure the coating there too.....
the rest is well known....
sincerely speedyG

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Re: Single density disks failing at a faster rate than ...

I've always kept a clean pressure pad. And I often wonder if this didn't help contribute to reliability; by keeping the surface clean and free of particles that could get wedged between the hard head and disk surface.

Eliminating those particles and getting them trapped in the pressure pad wad seems to have been a good thing. I've had only a handful of fails and just about all my disks are "converted" to double-sided via either a hole-punch, or write-protect switch "mod"..

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Re: Single density disks failing at a faster rate than ...

Hello Keatah,

it´s not the pad - but the dust cought up in the pad that executes the scratch on the surface.....
and even if you keep the pad clean ... i doubt that you are able to keep dust off from it....
the good luck is that in a clean house there is less dust around in the air....
and the coating on the old disks was rather thicker than at the newer ones...
as result of that the old ones last lonnger because it takes more time to scratch off the surface....
the only way to avoid that would be to clean with a vacuum cleaner....... ???
sincerely speedyG

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Re: Single density disks failing at a faster rate than ...

Well, I've always kept my disks in some sort of non-gassing plastic and stored them vertically. I've shaken them up from time to time to prevent settling. They're always used in a drive that is cleaned, perhaps cleaned too often! I don't stress or flex them too much either.

I basically follow the rules and symbols they print on some envelopes. I've got disks with seemingly hundreds of hours of continuous use, like my BBS logs and system disks. Especially the BBS logs!

I open the drive when the disk is not spinning (generally, sometimes). And I power up the drive and have it spinning before I put in a disk. No power spikes and no stickiness of the head or pad.

Sounds overkill, but all my 35 year old disks are operational. All these precautions are something I learned early on, the price to pay for getting rid of a cassette-based storage system I suppose.

And I enjoy my classic Apple II through either emulation or CFFA-style media or ADTpro. That means I can use fresh floppies as the workhorse and keep the originals another 30 years.

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Re: Single density disks failing at a faster rate than ...

I had better success reading a disk after I used a cotton swab and water to rub off some filmy substance on the cookie.

Everyone knows you can clean the disk drive. From my experience, you can clean the disk too!

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Re: Single density disks failing at a faster rate than ...

It's also interesting to note that I've got a carton of 500 twiggies and they were stored in the same environment as my other disks. However..however, the twiggies were in the same box as old photos. And guess what? The twiggies had some sort of powder deposition or some sort of mold or corrosion, I have no idea what. It seemed to brush off with the slightest touch of a q-tip, but there was a mottled stain below the dust I removed.

It wasn't a lot and was seemingly on the "exposed" surface where the heads were. I can only guess that the 40 year old pictures still out-gassed some chemical from the photo developing and printing process. Something that attacked the oxide. Or maybe the oxide acted as a catalyst for accumulation. I don't really know. It might have been simple moisture for all I know.

I'm not too disappointed or anything since I don't have equipment to read them.

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Re: Single density disks failing at a faster rate than ...

Hello Keatah,

just some info to understand better what you recognized..
1. Photos ( specialy older ones ) are coated with a film that is not antibiotic... i.e. on old pictures there is a good chance when stored in area with higher humidity and higher temperatures that bacteria start to grow in that coating.... they start "eating" the coating....

2. the same kind of storage conditions cause at the coating of magnetic media a process of oxidation ( rust )
of the metalic contents of the magnetic coating.... with long periods and changing temperature the top of the coating gets first micro-cracks and humidity can infiltrate and attack the coating material itself below and then the same thing happens like putting a nail in a glass of water.... when the metalic-content in the coating oxidates that causes in the following time the material itself to crack ....

thats exactly the reason that the companies told to keep media in dry humidity and at moderate temperatures...
sincerly speedyG

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Re: Single density disks failing at a faster rate than ...

We live in a high humidity climate, so that is probably at least partly responsible for the high failure rate. I do see a lot of mottling on disks - not all of them, but a little more all the time. I've even found it when opening new packages of disks in their original plastic - not that it is much of a barrier to humidity over the long term.

Oh well. Glad I have a couple of CFFAs. Wink

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Re: Single density disks failing at a faster rate than ...