Why is `private.img` kept around for volumes with `revisions_to_keep = 0`?

[qpost135]

@rustybird

There aren’t any relevant R4.2 changes in this area, AFAIK.

Assuming that @Johnboy had comparable workloads in R4.1 and R4.2 (as opposed to e.g. having a more fragmented volume image file in R4.2, as measured by filefrag), the only thing that comes to mind is that he incidentally moved to a newer kernel with the R4.2 upgrade, and that this new kernel version has some sort of pathological interaction with his SSD hardware.

I understood that the test of @Johnboy showed very clearly that the fresh install with default settings vs. BTRFS made all the difference. How could the kernel version have been the root cause, when he switched from a working non-BTRFS 4.2 to a broken BTRFS 4.2 and then back to a working non-BTRFS 4.2?

I’m also planning to do a reinstall with default settings within the next days.

Any settings I should/could check before doing this?