Re:M1 Mac owners are experiencing high SSD writes over short...
by scottlamb on Tuesday February 23, 2021 @09:23PM
(#26245870)
It also seems to me there are a couple jumps in the initial tweets here (particularly the assumption of the same write rate on 256 GiB models as on 2 TiB models). But regarding several of the assumptions you mentioned here:
> (4) that they are directly comparable to non-M1 hardware without further processing
> (5) that they do not increment when Time Machine or other filesystem snapshots occur
> (6) that they do not increment when APFS copy-on-writes occur
> (7) that they do not include the total byte size of sparsely-modified files
smartmonctl is a tool that inspects the drive's built-in statistics about physical writes. If it shows significant jumps from snapshots, copy-on-write, and sparse files, it's because those feature aren't working as designed in minimizing physical writes.
I also find it unlikely that a bug in smartmonctl or IOKit would show incorrect but plausible-looking values. More likely in the SSD's firmware. But I'm not getting alarmed just yet. (I also don't own an M1 Mac, so that's easy for me to say.)
> (4) that they are directly comparable to non-M1 hardware without further processing
> (5) that they do not increment when Time Machine or other filesystem snapshots occur
> (6) that they do not increment when APFS copy-on-writes occur
> (7) that they do not include the total byte size of sparsely-modified files
smartmonctl is a tool that inspects the drive's built-in statistics about physical writes. If it shows significant jumps from snapshots, copy-on-write, and sparse files, it's because those feature aren't working as designed in minimizing physical writes.
I also find it unlikely that a bug in smartmonctl or IOKit would show incorrect but plausible-looking values. More likely in the SSD's firmware. But I'm not getting alarmed just yet. (I also don't own an M1 Mac, so that's easy for me to say.)