Hacker News new | ask | show | jobs
by 8fingerlouie 1955 days ago
> That is two big assumptions: assuming linear degradation and assuming the mac is usable until it reaches 0%.

I thought i already accounted for that by stating "most users will get a decade of use". That's roughly 66% of linear degradation to 0%.

> and that by the time it is at least 90% on a 256gb or even 512gb SSD it will be effectivly unusable.

As i understand it, the "lifetime" is a reflection of the spare sectors, meaning once the spare sectors run out you'll start seeing errors instead of relocated sectors. It will probably continue for some time after that.

Knowing Apple, if it becomes a problem anytime within the first 5-6 years, they'll replace it for free. I had a 2008 iMac with a manufacturing problem on the Seagate 1TB drive it shipped with, and 5 years after purchase (2013), i was able to get the drive replaced for free despite my machine showing no signs of the error. 5 years after purchase, and a full 3 years after most consumer laws stop protecting you.

Other than that, the only reason this is a "problem" is because SSDs has an indicator that tells you when they'll expire. Spinning rust doesn't have that, but some spinning rust will also expire after 5-6 years, and most will have expired by the time a decade has passed (assuming daily usage).

1 comments

Lifetime is just "numbers of bytes written"/"expected lifetime bytes written"

There's a separate SMART attribute for remaining spare, and that is supposed to stay at 100% until you reach 100% lifetime, but the actual failure of cells can come sooner or later.

The scary conclusion I came to is based on the assumption of "expected lifetime bytes written" being proportional to SSD size (i.e. based on fixed Flash erase counts, which is usually how it goes); for the worst example we have so have, scaling his 3% from 2T to 256GB machines would mean some of those could be reaching 100% before the first year is up.