[Rdo-list] introspection and raid configuration

[Imre Farkas]

On 05/27/2015 09:50 AM, Dmitry Tantsur wrote:
> On 05/27/2015 09:38 AM, Imre Farkas wrote:
>> On 05/26/2015 05:43 PM, Dmitry Tantsur wrote:
>>> On 05/26/2015 04:42 PM, Imre Farkas wrote:
>>>> Hi all,
>>>>
>>>> I would like to gather some feedback on the current worfklow regarding
>>>> the subject. RAID configuration on DRAC machines works as follows (it
>>>> assumes there's no RAID volume on the machine):
>>>> 1. user defines the deployment profile and the target raid
>>>> configuration
>>>> for each profile
>>>> 2. ironic-discoverd introspects the node to gather facts
>>>> 3. ach-match picks a deployment profile based on the gathered facts
>>>> 4. instack triggers the raid configuration based on the selected
>>>> profile
>>>>
>>>> A bug[1] has been discovered regarding step 2: ironic-discoverd fails
>>>> because it tries to figure out the size of the local disk but it can't
>>>> find any as no volume exists on the RAID controller yet. This is a
>>>> chicken-and-egg problem because ironic-discoverd doesn't work if the
>>>> RAID volume(s) has not been configured but the RAID configuration can't
>>>> be triggered if ironic-discoverd hasn't gathered the facts about the
>>>> node.
>>>>
>>>> Few possible workarounds:
>>>> #1: make saving the local disk size optional in the standard plugin in
>>>> ironic-discoverd. The downside is that the standard plugin is supposed
>>>> to enroll nodes in ironic with all attributes necessary for scheduling.
>>>> This assumption might fail with this solution.
>>>
>>> -1 will never get upstream for the reasons you stated
>>>
>>>>
>>>> #2: run discovery multiple times with different set of plugins. The run
>>>> before RAID configuration would exclude the standard plugin while the
>>>> run afterwards could potentially exclude others. The parameters passed
>>>> by the user to ironic-discoverd for each run need to be properly
>>>> documented. It would slow down the installation because each run
>>>> requires a reboot which takes a lot of time on bare metal.
>>>
>>> Possible, but better (IMO) idea below.
>>>
>>>>
>>>> #3: name your suggestion!
>>>
>>> #3. modify your existing root_device_hint plugin to insert a fake
>>> local_gb value (with issuing a warning), and then put it to the
>>> beginning of the plugin pipeline. WDYT?
>>>
>>
>> I would avoid that for the very same reason as we rejected option #1: it
>> would do things quite differently than it is expected. However, building
>> on top of this idea, we could introduce a fake_local_gb plugin and
>> enable it as default in instack. Thoughts?
>
> ETOOMANYPLUGINS :D
>
> I would say it's fine for root_device_hint plugin. It's not enabled by
> default upstream, and it's a normal flow involving it.
>

Patch proposed: https://review.openstack.org/#/c/185896/

>>
>> Imre
>>
>>
>>>>
>>>> Any thoughts/preference on the above described workarounds?
>>>>
>>>> Thanks,
>>>> Imre
>>>>
>>>>
>>>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1222124
>>>
>>
>