HAMMER HEADS UP - 25-June-2008 - mirror core work may cause short term instability

[Matthew Dillon]

    I've done my best to keep the mirroring stuff separated out but some
    instability may have been introduced.  If any has it will be cleaned
    up by Friday.

    NOTE!  The mirroring utility is NOT ready for testing yet.  Using
    'hammer mirror-read <fs>' ought to be safe, it just serializes the <fs>
    to stdout.  Using 'hammer mirror-write <fs>' will likely result in
    fireworks.... lots of pretty multi-colored sparks, and a dead filesystem.

    --

    That said, I've gotten about 70% of the work done.  I still have a bunch
    of safeties to code up, the recursive update of the mirror_tid field
    in the B-Tree nodes isn't finished yet, and the related incremental
    mirroring feature (that uses the mirror_tid field) hasn't been coded
    into the utility yet either.  The incremental support will also make
    it possible to create continuous mirroring streams.

    Another nice little side-benefit that I hadn't thought of is that the
    mirror-read command, since it serializes the contents of a HAMMER
    filesystem, can be used as a 'dump' equivalent, and mirror-write can
    ultimately be used as a 'restore' equivalent.

						-Matt