...

• CopyCommand (from primary1 to secondary)
  • skipped.
  • check if there are other Command on same volume ?
• CopyCommand (from secondary to primary2)
  • check if volume exists on primary2 (via the host, other host on same cluster or pod or zone, depends on the scope of storage, or cluster of host)
  • check if volume is changed on primary2
    • if yes, still Copying
    • if no, update state
• CopyCommand (from primary1 to primary2)
  • check if volume exists on primary1
  • check if volume exists on primary2
  • check if volume is changed on primary2
    • if yes, still Copying
    • if no, update state
• MigrateVolumeCommand (from primary1 to primary2)
  • check if volume exists on primary1
  • check if volume exists on primary2
  • check if volume is changed on primary2
    • if yes, still Migrating
    • if no, update state

3.

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8 Limitations

• Assumption
  • Each request does not have multiple commands with same name
  • for example, 700028267079401857-org.apache.cloudstack.storage.command.CopyCommand
• Only support:
  • 3 commands
    • CopyCommand
    • MigrateCommand
    • MigrateVolumeCommand
  • resources in Migration state (vm, source volume, dest volume)
    • skipped if the resource state is not Migrating
    • skipped if the source or dest host/pool are inconsistent with command
  • Hypervisor: KVM
  • Storage: NFS, Local, Powerflex

3.

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9 To be Discussed (TODO)

1. How to distribute the reconciiation tasks if there are multiple management servers ?
   1. now: Reconciliation is processed by first management server
2. How to better handle the state DANGLED_IN_BACKEND ?
   1. now: no special action
3. How to better handle the state COMPLETED and FAILED ? Do not reconcile via hosts if state_by_agent to COMPLETED ?
   1. now: no special action

4. Test cases

4.1 Backend commands of some migration

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