The old default for this was lower but most modern versions of the ZFS defaults don’t hit this until the vicinity of 96% It’s not technically the little holes

The old default for this was lower but most modern versions of the ZFS defaults don’t hit this until the vicinity of 96% It’s not technically the little holes or even CoW that is the problem. It simply switched from a “first fit” to a “best fit” algorithm as it got full which was quite expensive to do the search for.