Comment by mustache_kimono

> Imagine that a directory ZAP has an entry that points to a bogus object ID. That would be an example. The ZAP block is intact but its content is inconsistent.

The above is interesting and fair enough, but a few points:

First, I'm not sure that makes what seems to be the parent's point -- that scrub is an inadequate replacement for an fsck.

Second, I'm really unsure if your case is the situation the parent is referring to. Parent seems to be indicating actual data loss is occurring. Not leaking objects or space or bogus object IDs. Parent seems to be saying she/he scrubs with no errors and then when she/he tries to read back a file, oops, ZFS can't.