[Openstack] Cut over from lvm_type=XXX to volume_clear=XXX

Jeffrey Walton noloader at gmail.com
Sun May 25 03:12:10 UTC 2014

On Sat, May 24, 2014 at 8:24 PM, John Griffith
<john.griffith at solidfire.com> wrote:
> On Fri, May 23, 2014 at 10:16 PM, Jeffrey Walton <noloader at gmail.com> wrote:
>> ...
>> Previous versions of OpenStack used 'lvm_type=default' to signify a
>> wipe. Current versions use 'volume_clear=zero' or
>> 'volume_clear=shred'.
>> For current versions, 'zero' is a single pass and writes 0's; while
>> 'shred' uses three passes of predetermined bit patterns.
>> When did the change occur from lvm_type to volume_clear?
> I think there's some confusion, lvm_type is not explicitly for setting
> secure delete.  The default lvm_type is still thick provisioned, and further
> in that case the default is still to do a zero of the entire volume.  None
> of the previous default behavior has changed.
> What has changed however is that ability to specify different types of
> delete or none at all and that was around the Grizzly time-frame.
> To reiterate, lvm_type has no direct link to the secure delete or
> volume_clear option.  Using thin however implicitly sets volume_clear=none
> as it makes no sense in that context.
> Hope that helps, sorry for any confusion and feel free to hit me up on IRC
> if you still have questions.
Thanks John. I appreciate the clarification. So I'm clear:

(1) lvm_type=default and volume_clear={zero|shred} does wipe the drive
(2) lvm_type=thin and volume_clear=none does *not* wipe the drive

What happens with:

(3) lvm_type=default and volume_clear=none
(4) lvm_type=thin and volume_clear={zero|shred}

I think (4) was already answered in the other thread, but I want to
make sure I understand the configuration matrix.

Also, am I understanding correctly: lvm_type handles block allocation
(meaning zeroization occurs during allocation if lvm_type=default);
while volume_clear handles block deletion (meaning wiping occurs
during deletion if volume_clear={zero|shred}). In essence, the
difference is a lazy deleter.

Thanks again for the help.


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