HWCloudEngine / storage-gateway

storage gateway to adapt cloud storage to replicate/snapshot/backup to other different cloud storage.
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[Designing] Read snapshot before it get replayed #8

Open yinweiishere opened 7 years ago

yinweiishere commented 7 years ago

Snapshot will be created by inserting a snapshot type journal and persist snapshot metadata in DR server. There will be a period between creation and snapshot journal to be replayed (how to ensure the ordering?). Issues:

  1. How to define snapshot created? 1.1 having persisted both journal and metadata; 1.2 snapshot journal being replayed; 1.3 snapshot journal has been replicated to remote; 1.4 snapshot journal has been replayed in remote site;

  2. If we define snapshot created as 1.1, remote snapshot created as 1.3, how to read/diff/roll back snapshot if it hasn't been replayed yet?

  3. For remote snapshot, we need make the replication pair volume with a snapshot as well in cinder, but with the same snapshot id as the local one: need rethink the replication pair design.