Comment 17 for bug 1022511

Reviewed: https://review.openstack.org/12521
Committed: http://github.com/openstack/cinder/commit/bb06ebd0f6a75a6ba55a7c022de96a91e3750d20
Submitter: Jenkins
Branch: master

commit bb06ebd0f6a75a6ba55a7c022de96a91e3750d20
Author: Pádraig Brady <email address hidden>
Date: Thu Sep 6 16:36:50 2012 +0100

    support a configurable volume wiping method

    Add a clear_volume() method that is called from delete_method().
    This is only implemented at present for the base LVM driver.
    This new clear_volume() method now supports these config vars:

      volume_clear = none, zero, shred
      volume_clear_size = size_in_MiB

    'zero' is the default method and unchanged from previously.
    'none' is used if security isn't a concern, or there is
      independent volume scrubbing.
    'shred' is for more security conscious situations where
    an overwrite count is required. Currently this defaults to 3 passes.

    size_in_MiB can be used to limit the cleared area to the first
    part of the volume, which can greatly speed up the operation,
    and can be useful with encrypted volumes for example where
    overwritting the encryption keys at the start is sufficient.

    Fixes bug: 1022511
    Change-Id: I7312678ff5d66156578501483a1b74e2a69e19a0