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 thecreate_configuration
step ofraid
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 thedelete_configuration
step ofraid
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 implementer 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 forraid.create_configuration
. This method will callupdate_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 forraid.delete_configuration
. This will setnode.raid_config
toNone
. Note thattarget_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¶
Implement Zapping States - https://review.opendev.org/140826
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.
References¶
[1] http://specs.openstack.org/openstack/ironic-specs/specs/approved/ironic-generic-raid-interface.html