• Joe Thornber's avatar
    dm: add thin provisioning target · 991d9fa0
    Joe Thornber authored
    Initial EXPERIMENTAL implementation of device-mapper thin provisioning
    with snapshot support.  The 'thin' target is used to create instances of
    the virtual devices that are hosted in the 'thin-pool' target.  The
    thin-pool target provides data sharing among devices.  This sharing is
    made possible using the persistent-data library in the previous patch.
    The main highlight of this implementation, compared to the previous
    implementation of snapshots, is that it allows many virtual devices to
    be stored on the same data volume, simplifying administration and
    allowing sharing of data between volumes (thus reducing disk usage).
    Another big feature is support for arbitrary depth of recursive
    snapshots (snapshots of snapshots of snapshots ...).  The previous
    implementation of snapshots did this by chaining together lookup tables,
    and so performance was O(depth).  This new implementation uses a single
    data structure so we don't get this degradation with depth.
    For further information and examples of how to use this, please read
    Signed-off-by: default avatarJoe Thornber <thornber@redhat.com>
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>