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Alex is right, wiping partition table is not enough. User can create
partition table with exact the same sizes of partition as was before. In
this case lvm may detect metadata on untouched partitions to assemble a
logical volume. We should remove lvm metadata from every partition (or wipe
1st megabyte of every partition).

--
Best regards,
Sergii Golovatiuk,
Skype #golserge
IRC #holser

On Tue, Dec 29, 2015 at 5:09 PM, Aleksandr Didenko <adidenko at mirantis.com>
wrote:

> > accurately wipe only partition table and do not touch any other data
>
> As Andrew said already, in such case LVM meta data will remain on the hard
> drive. So if you remove partition table, reboot the node (env reset), then
> configure exactly the same partition table (like when you use the same
> default disk allocation in Fuel), then Linux will find LVM info on the same
> sectors of HDD on re-created partitions and re-assemble old LVM devices
> automatically.
>
> Regards,
> Alex
>
> On Tue, Dec 29, 2015 at 4:25 PM, Artur Svechnikov <
> asvechnikov at mirantis.com> wrote:
>
>> Thank you all for the answers.
>> Well, it seems we should figure out how to do it another way. For now I
>> see only one solution - accurately wipe only partition table and do not
>> touch any other data. But this solution require huge changes in volume
>> manager and fuel-agent, so I don't like this solution. I'm trying to find
>> out better one so if you have any ideas please share it here.
>>
>> Best regards,
>> Svechnikov Artur
>>
>> On Tue, Dec 29, 2015 at 4:34 PM, Sergii Golovatiuk <
>> sgolovatiuk at mirantis.com> wrote:
>>
>>> Hi,
>>>
>>> Let me comment inline.
>>>
>>>
>>> On Mon, Dec 28, 2015 at 7:06 PM, Andrew Woodward <xarses at gmail.com>
>>> wrote:
>>>
>>>> In order to ensure that LVM can be configured as desired, its necessary
>>>> to purge them and then reboot the node, otherwise the partitioning commands
>>>> will most likely fail on the next attempt as they will be initialized
>>>> before we can start partitioning the node. Hence, when a node is removed
>>>> from the environment, it is supposed to have this data destroyed. Since
>>>> it's a running system, the most effective way was to blast the first 1Mb of
>>>> each partition. (with out many more reboots)
>>>>
>>>> As to the fallback to SSH, there are two times we use this process,
>>>> with the node reboot (after cobbler/IBP finishes), and with the wipe as we
>>>> are discussing here. These are for the odd occurrences of the nodes failing
>>>> to restart after the MCO command. I don't think anyone has had much success
>>>> trying to figure out why this occurs, but I've seen nodes get stuck in
>>>> provisioning and remove in multiple environments using 6.1 where they
>>>> managed to break the SSH Fallback. It would occur around 1/20 nodes
>>>> seemingly randomly. So with the SSH fallback I nearly never see the failure
>>>> in node reboot.
>>>>
>>>
>>> If we talk about 6.1-7.0 release there shouldn't be any problems with
>>> mco reboot. SSH fallback must be deprecated at all.
>>>
>>>
>>>>
>>>>
>>>
>>>>
>>>
>>>>
>>>
>>>> On Thu, Dec 24, 2015 at 6:28 AM Alex Schultz <aschultz at mirantis.com>
>>>> wrote:
>>>>
>>>>> On Thu, Dec 24, 2015 at 1:29 AM, Artur Svechnikov
>>>>> <asvechnikov at mirantis.com> wrote:
>>>>> > Hi,
>>>>> > We have faced the issue that nodes' disks are wiped after stop
>>>>> deployment.
>>>>> > It occurs due to the logic of nodes removing (this is old logic and
>>>>> it's not
>>>>> > actual already as I understand). This logic contains step which calls
>>>>> > erase_node[0], also there is another method with wipe of disks [1].
>>>>> AFAIK it
>>>>> > was needed for smooth cobbler provision and ensure that nodes will
>>>>> not be
>>>>> > booted from disk when it shouldn't. Instead of cobbler we use IBP
>>>>> from
>>>>> > fuel-agent where current partition table is wiped before provision
>>>>> stage.
>>>>> > And use disks wiping for insurance that nodes will not booted from
>>>>> disk
>>>>> > doesn't seem good solution. I want to propose not to wipe disks and
>>>>> simply
>>>>> > unset bootable flag from node disks.
>>>>>
>>>>
>>> Disks must be wiped as boot flag doesn't guarantee anything. If bootlag
>>> is not set, BIOS will ignore ignore the device in boot-order. More over, 2
>>> partitions may have bootflag or operator may set to skip boot-order in BIOS.
>>>
>>> >
>>>>> > Please share your thoughts. Perhaps some other components use the
>>>>> fact that
>>>>> > disks are wiped after node removing or stop deployment. If it's so,
>>>>> then
>>>>> > please tell about it.
>>>>> >
>>>>> > [0]
>>>>> >
>>>>> https://github.com/openstack/fuel-astute/blob/master/lib/astute/nodes_remover.rb#L132-L137
>>>>> > [1]
>>>>> >
>>>>> https://github.com/openstack/fuel-astute/blob/master/lib/astute/ssh_actions/ssh_erase_nodes.rb
>>>>> >
>>>>>
>>>>> I thought the erase_node[0] mcollective action was the process that
>>>>> cleared a node's disks after their removal from an environment. When
>>>>> do we use the ssh_erase_nodes?  Is it a fall back mechanism if the
>>>>> mcollective fails?  My understanding on the history is based around
>>>>> needing to have the partitions and data wiped so that the LVM groups
>>>>> and other partition information does not interfere with the
>>>>> installation process the next time the node is provisioned.  That
>>>>> might have been a side effect of cobbler and we should test if it's
>>>>> still an issue for IBP.
>>>>>
>>>>
>>> Since we do not use classical provision anymore, we have mco connection
>>> all the time. During IBP we have it as part of bootstrap, after reboot, mco
>>> is still present so all actions should be done via mco.
>>>
>>>
>>>>
>>>>>
>>>>> Thanks,
>>>>> -Alex
>>>>>
>>>>> [0]
>>>>> https://github.com/openstack/fuel-astute/blob/master/mcagents/erase_node.rb
>>>>>
>>>>> > Best regards,
>>>>> > Svechnikov Artur
>>>>> >
>>>>> >
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>>>>>
>>>>>
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>>>> --
>>>>
>>>> --
>>>>
>>>> Andrew Woodward
>>>>
>>>> Mirantis
>>>>
>>>> Fuel Community Ambassador
>>>>
>>>> Ceph Community
>>>>
>>>>
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