Linked by Thom Holwerda on Thu 27th Sep 2012 19:36 UTC
Apple I bought a brand new iMac on Tuesday. I'm pretty sure this will come as a surprise to some, so I figured I might as well offer some background information about this choice - maybe it'll help other people who are also pondering what to buy as their next computer.
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christian
Member since:
2005-07-06


I've got a few issues with your calculation. Obviously "ideal wear levelling" doesn't exist generically: what's ideal for one pattern is non-ideal for other patterns. And in fact a 128GB SSD is likely to be comprised of at least 8 NAND chips, which for performance reasons are running in parallel and may not take part in distributed wear leveling. So removing your assumptions might decrease your calculation by at least a factor of 8.


Of course, there's also write amplification as well to factor in.

But given how modern SSDs work (basically a log structured device) write amplification should be quite low (approaching 1) and wear leveling will actually be close to ideal once static wear leveling is employed.


We are also talking about reliability on it's own, but in real devices reliability is one of many conflicting goals: performance, capacity, cost, dimensions. etc. The point I'm trying to make is that it's not safe to make assumptions. Even if the MTBF was 100% accurate, it only describes a curve with a multitude of failure points. Even with 3-5 years MTBF, you can still fail in a few months time. I'm just recommending those with write-heavy data loads take extra precaution against data loss with flash drives.


My point was that for most people, you're unlikely to hit the FLASH p/e limit even with 3000 p/e cycles. Firmware issues are more likely to toast your data than physical FLASH errors, which I admit has been a problem with the early generations of drives. But firmware is getting better and the market more mature.

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