In message <200006152118.RAA26602@ghost.whirlpool.com>Andrew Gillham writes

>This implies that soft updates can break Qmail, much like Linux async
>filesystems might.  My understanding of the soft dependencies changes
>are that it is totally transparent and undetectable by an application.
>(e.g. the application has no way of knowing the metadata was not written
>synchronously to disk)
>Am I confused?  Is it safe to use soft updates under NetBSD for a mail
>server?

Andrew,

Try reading it this way:

qmail uses the local filesystem as stable storage.  If the local
filesystem guarantees that single-byte writes and directory operations
are atomic, then qmail orders its writes such that will never lose
mail except if the disk media itself dies.

Softdeps guarantee that the filesystem data and metadata is always
_consistent_, but doesn't guarantee that the bits go all the way down
out to disk synchronously at the point when the application issues
system calls.  So a softdep system could crash and leeve the on-disk
filesystem state consistent, but with qmail's "stable-storage"
operations still buffered.   "Don't do that".

that's what I think they're trying to say.