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Volume Mirroring (Havana Summit)

Avishay Traeger
Avishay Traeger

Volume mirroring allows for multiple consistent copies of volumes across storage entities to improve availability and disaster recovery. It provides a flexible framework where administrators can set up mirroring between storage pools within a single Cinder deployment or across multiple Cinder deployments for longer distance disaster recovery. Mirroring techniques vary in recovery point objective (RPO) and recovery time objective (RTO) depending on being synchronous, asynchronous, or periodic.

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Volume Mirroring Presenter: Avishay Traeger avishay@il.ibm.com IBM Research Haifa 息 2013 IBM Corporation
Agenda Goal Definitions Example flow 1: Single Cinder deployment HA, shorter-distance DR Example flow 2: Multiple Cinder deployments Longer-distance DR 息 2013 IBM Corporation
Goal Multiple consistent copies of selected volumes to mitigate failures of varying degrees Flexible framework for enabling mirroring technologies Where? Back-end: driver/storage Front-end: OS-level, hypervisor How? Several techniques for volume mirroring Biggest difference is RPO and RTO 息 2013 IBM Corporation
Recovery Point Objective (RPO) Recovery Time Objective (RTO) Recovery Point Objective How far back in time a disaster takes one RPO=0 synchronous copy Recovery Time Objective How long until operational after a disaster RTO=0 hot backup site 息 2013 IBM Corporation
Main technologies Synchronous Write to both copies before returning ACK Always consistent Asynchronous Write to primary, ACK, forward to secondary ASAP Periodic Accumulate changes and send to secondary periodically 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a volume_backend_name=pool1 volume_backend_name=pool2 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) Each may have one or more pools managed by Cinder which store volumes volume_backend_name=pool3 b 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a volume_backend_name=pool2 mirroring_unit_id=b volume_backend_name=pool3 mirroring_unit_id=b b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) Each may have one or more pools managed by Cinder which store volumes Drivers report id of mirroring participant (e.g., controller, file set) 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a Admin creates partnerships storage pairs with the potential to mirror between them volume_backend_name=pool2 mirroring_unit_id=b volume_backend_name=pool3 mirroring_unit_id=b b 息 2013 IBM Corporation
Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] Admin creates partnerships storage pairs with the potential to mirror between them Drivers report mirroring capabilities with each partner volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
Single Cinder deployment: User actions a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
Single Cinder deployment: User actions a 2 volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b User creates second volume, passes requirements in volume type, and first volume's id as scheduler hint. Candidates: any in a volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
Single Cinder deployment: User actions a 2 volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b User creates second volume, passes requirements in volume type, and first volume's id as scheduler hint. Candidates: any in a User creates a mirror relationship between the two volumes and optionally starts the copy 息 2013 IBM Corporation
Multi-Cinder deployment Local cloud_id = primary a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b Remote cloud_id = DRsite1 Consider two or more Cinder deployments Problem The mirror I/O is unchanged, but we can't control placement on the remote cloud and don't want the local driver calling the remote driver directly Solution Local Cinder communicates with a gateway, and the gateway calls public Cinder APIs on the other sites 息 2013 IBM Corporation

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Volume Mirroring (Havana Summit)

  • 1. Volume Mirroring Presenter: Avishay Traeger avishay@il.ibm.com IBM Research Haifa 息 2013 IBM Corporation
  • 2. Agenda Goal Definitions Example flow 1: Single Cinder deployment HA, shorter-distance DR Example flow 2: Multiple Cinder deployments Longer-distance DR 息 2013 IBM Corporation
  • 3. Goal Multiple consistent copies of selected volumes to mitigate failures of varying degrees Flexible framework for enabling mirroring technologies Where? Back-end: driver/storage Front-end: OS-level, hypervisor How? Several techniques for volume mirroring Biggest difference is RPO and RTO 息 2013 IBM Corporation
  • 4. Recovery Point Objective (RPO) Recovery Time Objective (RTO) Recovery Point Objective How far back in time a disaster takes one RPO=0 synchronous copy Recovery Time Objective How long until operational after a disaster RTO=0 hot backup site 息 2013 IBM Corporation
  • 5. Main technologies Synchronous Write to both copies before returning ACK Always consistent Asynchronous Write to primary, ACK, forward to secondary ASAP Periodic Accumulate changes and send to secondary periodically 息 2013 IBM Corporation
  • 6. Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) 息 2013 IBM Corporation
  • 7. Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) 息 2013 IBM Corporation
  • 8. Single Cinder deployment: Admin setup a b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) 息 2013 IBM Corporation
  • 9. Single Cinder deployment: Admin setup a volume_backend_name=pool1 volume_backend_name=pool2 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) Each may have one or more pools managed by Cinder which store volumes volume_backend_name=pool3 b 息 2013 IBM Corporation
  • 10. Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a volume_backend_name=pool2 mirroring_unit_id=b volume_backend_name=pool3 mirroring_unit_id=b b 2 storage entities in a single Cinder deployment (e.g., controller, file system) Mirroring is set up at a certain level (e.g., controller, file set) Admin must ensure network connectivity between mirror participants (e.g., a-b) Each may have one or more pools managed by Cinder which store volumes Drivers report id of mirroring participant (e.g., controller, file set) 息 2013 IBM Corporation
  • 11. Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a Admin creates partnerships storage pairs with the potential to mirror between them volume_backend_name=pool2 mirroring_unit_id=b volume_backend_name=pool3 mirroring_unit_id=b b 息 2013 IBM Corporation
  • 12. Single Cinder deployment: Admin setup a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] Admin creates partnerships storage pairs with the potential to mirror between them Drivers report mirroring capabilities with each partner volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
  • 13. Single Cinder deployment: User actions a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
  • 14. Single Cinder deployment: User actions a 2 volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b User creates second volume, passes requirements in volume type, and first volume's id as scheduler hint. Candidates: any in a volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b 息 2013 IBM Corporation
  • 15. Single Cinder deployment: User actions a 2 volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] 1 volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b User creates a volume, specifying mirror requirements in volume type: sync, active-passive. Candidates: any in a/b User creates second volume, passes requirements in volume type, and first volume's id as scheduler hint. Candidates: any in a User creates a mirror relationship between the two volumes and optionally starts the copy 息 2013 IBM Corporation
  • 16. Multi-Cinder deployment Local cloud_id = primary a volume_backend_name=pool1 mirroring_unit_id=a mirroring_capabilities=[b, [sync,async], active-passive] volume_backend_name=pool2 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] volume_backend_name=pool3 mirroring_unit_id=b mirroring_capabilities=[a, [sync,async], active-passive] b Remote cloud_id = DRsite1 Consider two or more Cinder deployments Problem The mirror I/O is unchanged, but we can't control placement on the remote cloud and don't want the local driver calling the remote driver directly Solution Local Cinder communicates with a gateway, and the gateway calls public Cinder APIs on the other sites 息 2013 IBM Corporation