--- Wendy Cheng <s.wendy.cheng@xxxxxxxxx> wrote:
> Ja S wrote:
> > Hi, All:
> >
> > >From some online articles, in ext3, there are
> journal,
> > ordered, and writeback three types of journaling
> file
> > systems. Also in ext3, we can attach the
> journaling
> > file system to the journal block device located
> on a
> > different partition.
> >
>
> GFS *is* a journaling filesystem, same as EXT3. All
> journaling
> filesystem has journal(s) which is (are) almost an
> equivalence of
> database logging. The internal logic of journaling
> could be different
> and we call it journaling "mode".
> > I have not yet found related information for GFS.
> >
> > My questions are:
> >
> > 1. Does GFS also support the three types of
> journaling
> > file systems? If not, what journaling file system
> is
> > used in GFS?
> >
> So please don't use "journaling file system" to
> describe journal.
> Practically, GFS has only one type of journaling
> (write-back) but it
> supports data journaling thru "gfs_tool setflag"
> command (see "man
> gfs_tool). GFS2 has improved this by moving the
> "setflag" command into
> mount command (so it is less confusing) and has been
> designed to use
> three journaling modes (write-back, order-write, and
> data journaling,
> with order-write as its default). It (GFS2),
> however, doesn't allow
> external journaling devices yet.
>
> I understand moving ext3 journal into an external
> device and/or moving
> journaling mode from its default (order write) into
> "write back" can
> significantly lift its performance. These tricks can
> *not* be applied to
> GFS.
Thank you very much indeed for the clarification.
Jas
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