Over the past week, some M1 Mac users have been reporting alarming SSD health readings, suggesting that these devices are writing extraordinary amounts of data to their drives (via iMore).
Across Twitter and the MacRumors forums, users are reporting that M1 Macs are experiencing extremely high drive writes over a short space of time. In what appear to be the most severe cases, M1 Macs are said to be consuming as much as 10 to 13 percent of the maximum warrantable total bytes written (TBW) value of its SSD.
Flash memory on solid-state drives, such as those used in Macs, can only be written to a certain number of times before they become unstable. Software ensures that load is spread evenly across the drive's memory cells, but there is a point when the drive has been written to so many times that it can no longer reliably hold data. So while SSD wear is normal, expected behavior, drives should not be exhausting their ability to hold data as quickly as some M1 Macs seem to be.
One user showed that their M1 Mac had already consumed one percent of its SSD after just two months, while another M1 Mac with a 2TB SSD had already consumed three percent. The total data units written for these machines is running into many terabytes, when they would normally be expected to be considerably lower.
16GB M1 MBP, 2TB SSD, 2 months in. pic.twitter.com/SaSmieaT1s — David (@david_rysk) February 15, 2021
The user with three percent usage speculated that, were his machine a 256GB model, it could have used as much as 30 percent to date, and have reached maximum TBW in around two years. An SSD can continue to function once its TBW limit has been reached, but there is no knowing how long it will last past this point.
It is not known how widespread the TBW issue is, but reports of strange SSD behavior are also now emerging from users with Intel-based Macs, suggesting that the TBW issue may not be exclusive to M1 Macs.
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.
