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So how long might the Flash drive in a (pricey) MacBook Air last?
  So Apple is now offering a 64GB Flash-based drive (aka SSD, or solid state drive) as an option on the MacBook Air.

But here's the thing: it's known (because people murmur it) that Flash has a limited life, because the number of times you can write to a block of storage is limited. At some point, the capacitance breaks down and it won't hold the charge any more. Bzzt, that bit of memory is gone.

But how long would that be? A long (and recast) analysis by Starage-search.com looks at SSD Myths and Legends, and notes that

In the early days of flash SSDs managing this was a real headache for oems and users. The maximum number of write cycles to an address block - the endurance - was initially small (about 10,0000 10,000 [corrected - CA] write cycles in 1994, rising to 100,000 in 1997). And the capacity of flash storage was small too. So the write endurance limit was more than just a theoretical consideration. In the worst case - you could destroy a flash SSD in less than a week!

Don't worry, though, things have moved on. Apart from anything, there's much more storage now, so any given block is less likely to reach its maximum read/write capacity.

So in May 2006 he looked at what would happen with an SSD used by a bonkers data recorder that kept on overwriting and rewriting and erasing data on the drive. Fortuitously for us, he chose a 64GB drive.

We assume perfect wear levelling which means we need to fill the disk 2 million times to get to the write endurance limit.

2 million (write endurance) x 64G (capacity) divided by 80M bytes / sec gives the endurance limited life in seconds.
That's a meaningless number - which needs to be divided by seconds in an hour, hours in a day etc etc to give...
Can you see how big it is yet? Let's divert for a moment to an article written in 2007, Debunking Misconceptions in SSD Longevity which also drew on that analysis:

Assuming a much smaller endurance rating of 100,000 cycles (typical rating quoted by NAND flash vendors), a bigger volume of writes per day at 3.4TB and no caching nor wear leveling implementations, a 160GB solid state drive is projected to last up to 12.9 years, which is definitely longer than the average replacement cycle of most IT storage devices and equipment.

And since you were wondering, the time before your 64GB SSD is hosed in the above implementation is 51 years.

If your SSD-equipped MacBook Air is still in use 12 or especially 51 years from now, then you might need to be able to replace the drive.
release time:1/18/2008
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