M1 Mac users report alarming hard drive health readings

Macbook Air M1
Macbook Air M1 (Image credit: Daniel Bader / iMore)

What you need to know

  • M1 Mac users are reporting extremely troublesome health readings from their SSDs.
  • The TBW (total bytes written) figures show the life spans of these hard drive scould be in real danger.
  • There is hope however that a software bug is behind the issue.

There are numerous reports from M1 Mac users that macOS is giving out worrying hard drive health reports which could indicate severe life span problems.

From the LTT forums:

Some more professional users of the new M1 Macbooks are experiencing extremely high drive writes over relatively short time.The most severe cases have "consumed" about 10-13% of the maximum warrantable TBW value of the SSDs (given their capacity & using values for equivalent market-available NVMe drives).

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The issue of 'TBW', or total bytes written, refers to the lifespan of an SSD. As explained by PC Gamer:

Core to what's going on is the way in which SSDs work, specifically the number of writes they can reliably support. The flash memory on the drives can only be written to a certain number of times before becoming unstable. There are plenty of systems in place to spread the load across all the memory cells, but essentially there's a point where the drive has been written to so many times that it can no longer reliably hold the information.This is all summed up by the Total Bytes Written figure, measured in terabytes (which is why it's also referred to as Terabytes Written). This needs to be considered in the context of the length of the warranty, which is generally five years.

If the readings being given out from these machines is correct, developer Hector Martin says it could indicate that some machines "aren't going to last half a year":

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Martin does however state this is "definitely" a bug, however its unclear if that relates to the readings being given, or macOS behavior which is causing the readings to be abnormally high (but accurate). As PC Gamer notes in its report, smart monitoring tools "are notorious for misreporting" and this could be an M1 teething problem.

An update from Hector last week noted M1 SSD isn't proportional to driver size, so the "less than one-year" scenario is very unlikely:

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Martin described this as "still way too fast, but not as bad as we previously thought". Martin further notes that the problem isn't exclusive to the M1 Mac, and that some Intel users have also been seeing strange readings. Most recently, Dan Seifert on Twitter:


Seifer noted the issue was "all swap" caused by a 'Hand Mirror' app, and that closing it meant he could watch his SSD "reclaim free space in real time".

SSDs can continue to operate once the TBW limit is reached, however, there is no guarantee as to how long it can last. As such, Apple will no doubt be working on a fix for this in macOS, either to fix faulty readings or to rectify the behavior behind them.

Stephen Warwick
News Editor

Stephen Warwick has written about Apple for five years at iMore and previously elsewhere. He covers all of iMore's latest breaking news regarding all of Apple's products and services, both hardware and software. Stephen has interviewed industry experts in a range of fields including finance, litigation, security, and more. He also specializes in curating and reviewing audio hardware and has experience beyond journalism in sound engineering, production, and design.

Before becoming a writer Stephen studied Ancient History at University and also worked at Apple for more than two years. Stephen is also a host on the iMore show, a weekly podcast recorded live that discusses the latest in breaking Apple news, as well as featuring fun trivia about all things Apple. Follow him on Twitter @stephenwarwick9