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[OM] Re: First CF card failure

Subject: [OM] Re: First CF card failure
From: Tim Hughes <timhughes@xxxxxxxx>
Date: Sun, 28 Oct 2007 16:22:24 -0700 (PDT)
Some **chips** now routinely have a million cycle erase/write capability. 
There are now **cards** rated at a much larger number of erase/writes, but 
surprise they cost more
and are generally aimed at non-camera use. 
To make these more reliable they do all sorts of tricks over and above 
leveling, but specifically
they add more redundancy and extended reed-solomon coding error detection and 
correction, just
like they do on hard disks!  They even add spare memory sectors that can be 
mapped in when the
error rate gets so high, so the the R-S coding cannot do the corrections.  One 
problem is how the
"boot sector" is handled since this needs to work more reliably than the rest 
for the "disk" for
everything to work long term. 

A number of cf vendors for consumer cameras etc now warranty their drives for 
5years or even 8
years figuring you wont keep the paperwork and you wont be interested in what 
is then a small
drive after 4years! My guess is they rely on consumers being lazy rather than 
having so much
better technology. It is a bit like warranteed car batteries.

With the gradual move away from magnetic HD's as seen in high end Dell laptops 
using flash memory
that became available in July , I would guess higher reliability flash memories 
will become more
commonly available.  

Tim Hughes

--- Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:

> When I said this was my first CF card failure I wasn't telling the 
> complete story.  This was my first CF card failure where the CF card was 
> being used in a camera.
> 
> Some number of years ago when a 64MB CF card was considered new and 
> huge I happened to be the engineering design manager for a small company 
> developing products for the US Navy.  One of the products we made was a 
> navigational display for aircraft carriers which incorporated a small 
> computer and hard drive and a color LCD panel.  One of our major 
> problems with products for the Navy was getting them past the shock 
> test.  In short, the product was bolted to the deck of a barge floating 
> in a rock quarry where a 60 pound charge of dynamite was set off next to 
> the barge.  The requirement was that the product had to be running and 
> fully functional before and after the explosion.  Hard drives and glass 
> display panels tend to take not too kindly to this test.  Since 64MB CF 
> cards had just come on the market we considered them large enough to 
> take the place of the hard drives.  Being solid state we figured it 
> would be much more likely to survive the shock test.  In the process I 
> had to investigate the likely life of the cards.  I don't know what it 
> is today but back then a CF card sector was typically quoted as having a 
> life of 100,000 write cycles which is facilitated by wear leveling. 
> Wear leveling is a process whereby heavily used sectors are logically 
> swapped for infrequently used ones so that the wear is distributed 
> evenly across  the card.  We figured 100,000 write cycles was way more 
> than enough since the disk was mainly a program loading device with very 
> little write activity.  We eventually did encounter a few premature 
> failures at sea but our product inspections indicated it was most likely 
> due to curious techie sailors who couldn't keep their hands out of the 
> gear.
> 
> Anyhow, the manufacturers claims at the time were for 100,000 write 
> cycles for each sector.  That says you'd have to fill your CF card 
> 100,000 times before it fails.  The 128MB card I first wrote about was 
> unlikely to have had been filled even 50 times.
> 
> Chuck Norcutt
> 
> Bob Whitmire wrote:
> > Thanx. Figured as much. Just read somewhere else that CF cards (or  
> > any in-camera image storage, for that matter) have a limited  
> > lifespan, perhaps more limited that we might tend to think. Wish I  
> > could recall where I read it.
> > 
> > --Bob
> > 
> > 
> > On Oct 28, 2007, at 12:02 PM, Chuck Norcutt wrote:
> > 
> >> Just to let you know that, tough as they are, they do eventually fail.
> > 
> > 
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