Solid state disks are a lot faster than hard disk drives but one of the downsides of this technology is that NAND cells wear out over time. One simple metric that offers a clue about how long a disk will last is terabytes written (TBW), which is the total amount of terabytes of data that an SSD can write before it reaches the end of its promised lifecycle. SSD firmware tries to spread the load evenly over all cells, but after a certain point an SSD can no longer reliably store data.
Various figures are flying around Twitter, with lots of users reporting that even with limited use, M1-based Macs have already consumed several percent of the maximum warrantable total bytes written (TBW) value over the course of two to three months.
In the most severe cases, users are reporting their M1-based Mac has already used 10 to 13 percent! The implication here is that if this SSD behavior continues, some of these disks may last under two years. And as the disk is soldered to the PCB, it can't be easily replaced.
MacRumors reports it's unknown whether the high SSD consumption is by design -- or whether it's a bug. The site writes there are some messages that indicate it may not be limited to the M1-based devices, and that Intel-based Mac systems could be affected too:
The reported wear is so extreme on some ?M1? Macs that it suggests the problem is due to a bug rather than the expected behavior of the ?M1? chip, but it is unclear if the problem pertains to erroneous readings or macOS genuinely writing vast amounts of data to the drive. Drive monitoring tools are sometimes unreliable and it is likely that the issue can be fixed via an update to macOS Big Sur.
16GB M1 MBP, 2TB SSD, 2 months in. pic.twitter.com/SaSmieaT1s— David (@david_rysk) February 15, 2021