lightos volume driver spec
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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===============================
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Lightbits LightOS(TM) Nova Spec
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===============================
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https://blueprints.launchpad.net/nova/spec/nova-support-lightos-driver
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Lightbits Labs(TM) (http://www.lightbitslabs.com) LightOS(R) is software-defined,
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cloud native, high-performance, scale-out and redundant clustered NVMe/TCP
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storage that performs like local NVMe flash.
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The nova Lightbits LightOS libvirt volume driver works with LightOS
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support for cinder and os_brick to enable openstack environments using
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nova/libvirt to connect to LightOS storage clusters.
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Problem description
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===================
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LightOS provides persistent volume storage. In normal flow, cinder
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triggers volume creation/deletion and attachment/detachment through
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the nova libvirt LightOS volume driver. In abnormal conditions (e.g.,
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when the nova node has gone down for reboot or power failure and then
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come back up, or on nova restart) the volume driver queries which
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instances exist on startup and what storage they were connected to (if
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any). For any instances that were connected to LightOS, the libvirt
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LightOS volume driver together with the os_brick LightOS connector
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will reestablish the connection to LightOS for those instances and
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volumes.
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Use Cases
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---------
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As an operator I would like to leverage LightOS with openstack to get
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highly-performing (performs the same as local NVMe SSDs) remote
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storage over NVMe/TCP for my openstack clouds, with failure-resistance
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both on the storage drive level and the storage server level. I want
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the performance of local NVMe drives with the convenience and
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flexibility of remote storage, while knowing that I am secure and my
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instances will remain connected to their storage even if drives and
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storage nodes fail.
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Proposed change
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===============
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We add a new libvirt volume driver to nova that will provide
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functionalities of attach, detach and extend to a LightOS cluster
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volume, as well as querying which instances exist on startup (e.g.,
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after reboot of power failure). This is being added concurrently with
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the LightOS support for cinder and for os_brick.
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NVMe/TCP volumes are host mounted. The os_brick connector connects as
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needed to the LightOS cluster via NVMe/TCP and exposes host device
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files to the nova node. From the libvirt/QEMU point of view, the files
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are then attached/detached to instances.
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Although LightOS works with VMware and other container and
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virtualization environments as well, LightOS openstack support is
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limited to libvirt-based environments.
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Live migration with multi-attach is fully supported and there are no
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special network requirements. LightOS works via NVMe/TCP that works
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over any TCP/IP network. The LightOS cluster needs to be reachable
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(routable) over TCP/IP from the compute nodes and network bandwidh
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should be provisioned to support the desired storage traffic.
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Alternatives
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------------
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None
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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The LightOS volumes are first mounted by the libvirt host, which then
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passes them to QEMU as local host files to attach/detach to
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instances.
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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LightOS cluster must be installed and configured and the The Lightbits
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Labs discovery-client service must run on compute nodes. For more
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details, see the README included with the cinder driver:
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https://review.opendev.org/c/openstack/cinder/+/821602
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Developer impact
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----------------
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None
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Upgrade impact
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--------------
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Generally, there is no impact on upgrades.
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During rolling upgrades where some compute nodes may have been upgraded
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with LightOS support and some haven't been upgraded yet, the operator should
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use either traits or use a placement aggregate to make sure cinder only places
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instances using LightOS storage on nova-computes that have been updated.
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Implementation
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==============
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Assignee(s)
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-----------
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Yuval Brave (yuval@lightbitslabs.com)
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Feature Liaison
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---------------
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None
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Work Items
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----------
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* create a new volume driver for lightos
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* upgrade os-brick to use a new os-brick with the LightOS connector
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Dependencies
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============
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The LightOS libvirt volume driver requires the corresponding LightOS
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cinder driver and os_brick support. Cinder blueprint is at:
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https://blueprints.launchpad.net/cinder/+spec/cinder-lightos-driver
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https://review.opendev.org/c/openstack/cinder/+/821602
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https://review.opendev.org/c/openstack/os-brick/+/821603
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Testing
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=======
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Unit tests were added to the patch. Lightbits LightOS third party CI
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is hosted by Lightbits Labs.
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Documentation Impact
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====================
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Documentation for configuring lightos storage will be added to:
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https://review.opendev.org/c/openstack/cinder/+/821602/10
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References
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==========
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None
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History
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=======
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.. list-table:: Revisions
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:header-rows: 1
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* - Release Name
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- Description
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* - Yoga
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- Introduced
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