> ZFS must support POSIX semantics, part of which is hard links. Hard
> links allow you to create multiple names (directory entries) for the
> same file. Therefore, all UNIX filesystems have chosen to store the
> file information separately for the directory entries (otherwise, you'd
> have multiple copies, and need pointers between all of them so you could
> update them all -- yuck).
For what it's worth, some file systems have chosen to special-case hard links
because they are rare and the directory/inode split hurts performance. Apple's
HFS is a case in point. The file metadata ("inode") is part of the directory
entry,
so that no additional disk access is required to retrieve it. If the file is a
hard
link, this metadata is a pointer to the shared metadata for the file.
Anton
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