[Rdo-list] introspection and raid configuration

[Imre Farkas]

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?

Imre


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