On Mon, 5 Jun 2000, Andi Kleen wrote:
> On Mon, Jun 05, 2000 at 10:40:05AM -0700, Chris Mason wrote:
> > > > Yes, ext3's jfs and reiserfs have the same fundamental
> > ideas.
> > > > block based write ahead logging. With slight modifications to the jfs,
> > > > wandering logs could even fit in.
> > >
> > > What are wandering logs, if I might ask?
> > >
> >
> > This is an idea from Hans. Instead of having a dedicated logging area on
> > the disk, any block can be a log block. Unlike ext2, reiserfs metadata
> > can be anywhere on the disk. Placement of these tree nodes is critical to
> > performance, and the wandering logs idea allows you to log the block by
> > simply writing it to a new (better) location. So, the metadata is
> > effectively defragmented on the fly.
>
> And how do you find the log spread out over disk ?
Well, Hans' original idea was to have another set of bitmap blocks on the
disk, and to use them to denote which blocks were log blocks. Whoever
implements the wandering logs (it will be someone working on the v4 code),
might be able to find another way.
-chris
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