How worn is your Mac's SSD, and should you be worried?

Concerns that Macs powered by M1 Apple Silicon might suffer premature SSD wear has prompted other Mac users to wonder how worn their storage is.

Like everything, SSDs (Solid State Drives) wear over time. But because it's component that's buried inside your Mac that runs silently, it can be tricky to know when it's getting bad. And since "bad" with respect to storage can mean data loss, understandably, people worry.

Losing data is the worst.

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Recently, reports emerged that M1 Apple Silicon powered Macs might be suffering from premature SSD wear. The reason is unknown, and as of yet Apple has not commented or released a patch in relation to this issue.

Is it a problem? Well, excessive wear is never a good thing, and it's not a good look, but as I'll come to in a bit, it's not the three-alarm issue that the media made it out to be.

But the M1-Macs are new. What about your old Mac that has an SSD inside, holding your precious data? 

How worn is that?

SSD wear is measured in TBW, or TeraBytes Written. It's a feel-good number that storage manufacturers come up with to measure hardware life (think MTTB for Mean Time Before Failure for hard drives).

Typically, a 250GB SSD will have a rating of 60 and 150TBW, which means that even at the lowest end of the rating to exceed this number in a year you'd have to be writing more than 100GB of data onto that 250GB drive EVERY DAY.

This rating is also a conservative estimate. I've seen drives far exceed it. I've also seen drives die prematurely (but often this is not related to TBW).

Also, manufacturers are now offering higher levels of TBW -- like Samsung's 600TBW rating backed by a 10-year warranty -- so this is rapidly becoming a non-issue.

OK, but you still want to know how worn your SSD is. How do you do this?

There are three things you can do.

  1. Don't worry about it
  2. OK, if you're worried, download and install Homebrew, as described here (just download the command line tools)
  3. Download DriveDX

Personally, I like DriveDX. There's a free trial that'll give you an at-a-glance view of how worn your SSD is. A full license only costs $20, so it actually a good utility to have installed.

Two indicators to look at in DriveDX are Life Percentage Used and Data Units Written, both under Health Indicators.

DriveDX analysis of the SSD inside a 2018 MacBook Pro

DriveDX analysis of the SSD inside a 2018 MacBook Pro

Simple.

All this said, I wouldn't get too worried about drive wear. Most dead SSDs I've come across have died well before hitting their TBW rating. There are plenty of other things to go wrong.

Also, back up your data, so the inconvenience of a dead drive doesn't turn into catastrophic data loss.