MacOS 11 excessive SSD write wear

As noted by Hector Martin and others, MacOS 11 appeared to have a possible kernel bug causing excessive SSD write wear whenever the SSD was in the “on” state. One can use “smartmontools” to check SSD write history:

brew install smartmontools

smartctl --all /dev/disk0

Note that SSD on state time can be much less than Mac powered-on time, particularly if the Mac is sitting idle. This is especially the case for the Mac Mini, which may sit powered on but unused for the majority of the time by some users.

Thankfully as noted by Jonas Ribe, Hector Martin and others, MacOS 11.4 appears to have fixed this SSD write bug:

Thankfully we haven’t see the 100+ TB of excess SSD wear pre-11.4 as Jonas did. We saw less than 5TB of excess wear on each of our mostly idle, continuously powered on Mac Minis.

Again, tentatively this problem is resolved by MacOS 11.4.