UFS2 Journaling implementation detail

[Ivan Voras]

2008/4/19 Unga <unga888 at yahoo.com>:
> --- Ivan Voras <ivoras at freebsd.org> wrote:
>
>
> > No, gjournal is a layer below the file system (think
>  > of it as a virtual disk drive) that does
>  journalling.
>  > You need to create a file system on top of gjournal.
>
>  > Pawel added some necessary integration for UFS.
>  >
>  Since the gjournal is block level journaling, not file
>  system level journaling, can one journal be used to
>  cover two or more partitions?
>
>  Example:
>  gjournal label -c ad0s4e ad0s4d
>  gjournal label -c ad0s4f ad0s4d
>  gjournal label -c ad0s4g ad0s4d
>
>  newfs -J /dev/ad0s4e.journal
>  newfs -J /dev/ad0s4f.journal
>  newfs -J /dev/ad0s4g.journal
>

Unfortunately not, the most you can do is divide that one partition
into more partitions and use each of those separately for each file
system.

Most of those limitations (journal size, usage, etc.) stem from the
fact that gjournal is not "proper" file system journaling in the sense
that it's implemented outside of the actual file system and is
basically independent from it. A "proper" journalled UFS (like Sun's)
would behave nicer.