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I think you are correct about the C and D. Considering replication is currently asynchronous it is clear that we cannot really talk about C.
by alexpopescu 17y ago
I think you are correct about the C and D. Considering replication is currently asynchronous it is clear that we cannot really talk about C.
- JulianMorrison 17y agoAsync replication can be consistent if it preserves transaction ordering and boundaries. In MongoDB that boundary is around each one update/insert operation. So async replication isn't the consistency loss - the problem is that transaction boundaries are only weakly respected within one operation. The old data is not preserved while its new value is being written. Catastrophic shutdown could leave a record half-altered.