The question being asked in the following article is, how many times can you write to one of these little Flash drives before the Flash memory fails?
His conclusion is that these drives can handle nearly a hundred million write cycles. The drives incorporate a "wear leveling" feature, so files being written are moved around to prevent a Flash memory cell from failing. It's an interesting article.
Why is this an issue at all? Why can't flash memory be written to indefinitely? If you look at How Flash Memory Works you can understand how the writing process works.
For more detail, jump forward to the 20:30 point in this video.
The problem is that all of this high-voltage work eventually "wears out" the oxide of the cell and ruins the tunneling effect. this article also talks about read disturbs:
When a bit is read, there is a chance that it can change the state of an adjacent bit.The more times a bit is read, the greater the likelihood that it will flip an adjacent bit. As with other bit errors, the probability that a read disturb will occur also depends upon the number of P/E cycles that a block has experienced.
The other aspect of a flash memory is aging. If you write data to a flash drive and stick it in a drawer, will the data still be there 5 years later? 10 years? The maximum life of the data appears to be somewhere between 5 and 10 years.
This brings up a good question - if you want to store data for the long haul (say a century or more) , how might you do it? We'll answer that in another question.
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