VMFT - Primary-backup replication

Overview

• virtual machines layers
• replication in different layers
• e.g., replicating GFS master

Approaches

• pause, replicate states, continue
• easy to implement
• state machine, replicate inputs
• efficient in performance

Non-determinism

• clock
• record
• multi-core (different from multi-thread)
• not supported in vmft
• IO race
• non-blocking
• DMA

Input/Output consistency

• exactly once over network? (TCP, UDP)
• disk read

Network partition and “split-brain”

• failure detector
• atomic compare and swap
• can lease solve the problem?