[loeg]

> For those unfamiliar with the terminology this is just confusing, and for those that are familiar this discussion is all fundamental and well known anyway.

Eh, agree to disagree.

> Unfortunately for COW filesystems including zfs and btrfs fallocate doesn’t do anything useful for preallocation.

Both ZFS and BtrFS have "nocow" modes that are probably more suitable to this type of use case. And other filesystems are widely used.

[finnh]

Can you point me to docs for ZFS offering a nocow mode? I haven't used it in about a decade, but i can't see how that would work - wafl/cow is a pretty fundamental invariant in everything ZFS does