In-band RAID configuration using agent ramdisk

https://bugs.launchpad.net/ironic/+bug/1526398

This spec proposes to implement a RAID configuration interface using Ironic Python Agent (IPA). The drivers agent_ipmitool, agent_pyghmi, agent_ssh, agent_vbox and agent_ilo drivers will make use of this new implementation of RAIDInterface.

Problem description

Currently there is no way in Ironic to do RAID configuration for servers using in-band mechanism.

Proposed change

This spec proposes to implement in-band RAID configuration using IPA. It proposes to implement the RAIDInterface as mentioned in the parent spec [1]. The implementation will be named AgentRAID. The main job of the implementation will be to invoke the corresponding RAID operation methods on agent ramdisk. Interested vendors will implement these methods in Ironic Python Agent using hardware managers.

Following are the changes required:

  • The following methods will be implemented as part of AgentRAID:

    • create_configuration - This will create the RAID configuration on the bare metal node. The following are the steps:
      • Uses clean.execute_clean_step command in Ironic Python Agent ramdisk to invoke the create_configuration step of raid interface.
    • delete_configuration - This will delete the RAID configuration on the bare metal node. The following are the steps:
      • Uses clean.execute_clean_step command in Ironic Python Agent ramdisk to invoke the delete_configuration step of raid interface.
  • RAID configuration will be limited to zapping only at first by hardcoding its clean step priority to be 0. We’ll consider interaction with cleaning mechanism later. This allows us to make target_raid_config mandatory for the new clean steps.

  • When the agent ramdisk is running an in-band clean step, the conductor gets the status of the last in-band clean step on every heartbeat. When an in-band clean step completes, the conductor resumes the cleaning and goes on to the next clean step if any. A new mechanism - the agent_base_vendor.post_clean_step_hook decorator, will be added. This allows a driver implementor to specify a function to be invoked after successful completion of an in-band clean step (and before the next clean step is started). The decorated function would take two arguments: the task and the command status (of the clean step) returned by the agent ramdisk.

    For example:

    @agent_base_vendor.post_clean_step_hook(
        interface='raid', step='create_configuration')
    def _create_configuration_final(task, command):
  • A method agent._create_configuration_final will be added as a post clean step hook for raid.create_configuration. This method will call update_raid_info with the actual RAID configuration returned from the agent ramdisk.

  • A method agent._delete_configuration_final will be added as a post clean step hook for raid.delete_configuration. This will set node.raid_config to None. Note that target_raid_config will be left intact, and will be reused by future zapping calls.

  • It is possible to have a hardware manager that does software RAID configuration, but it goes beyond the scope of this spec, as it requires RAID configuration to be run as a clean step after disk erasure.

Alternatives

Some bare metal servers do not support out-of-band RAID configuration. They support only in-band raid configuration. I don’t see any other alternatives other than making use of a ramdisk to do this.

We could provide an option to enable RAID as part of cleaning. However, this will make target_raid_config mandatory for all nodes managed by a given conductor. We’ll have to reconsider it later.

Data model impact

None.

State Machine Impact

None.

REST API impact

None.

Client (CLI) impact

None.

RPC API impact

None.

Driver API impact

None.

Nova driver impact

None.

Ramdisk impact

N/A

Security impact

None.

Other end user impact

None.

Scalability impact

None.

Performance Impact

None.

Other deployer impact

None.

Developer impact

Other hardware vendors developing drivers for OpenStack can use Ironic Python Agent for in-band RAID configuration. They can add their own hardware manager implementing the method and get the RAID configuration done.

Implementation

Assignee(s)

rameshg87

Work Items

  • Implement the mechanism for post clean step hook.
  • Implement AgentRAID

Dependencies

Testing

Unit tests will be added.

Upgrades and Backwards Compatibility

None.

Documentation Impact

None. Most of the RAID configuration details in Ironic are covered in the parent spec. If anything is required in addition, respective vendors making use of AgentRAID will need to document it.