How would you implement fault-tolerant data logging, ensuring no data loss during failover?

How would you implement fault-tolerant data logging, ensuring no data loss during failover?

• A. Single-channel logging to a single media.
• B. Redundant logging channels, replication to multiple media, journaling and commit protocols, sequence numbering and integrity checks.
• C. Disable logging on failover.
• D. Rely on volatile memory for logs.

Answer: (B)

Fault-tolerant data logging hinges on providing multiple independent paths and ensuring durability for every write so nothing is lost during failover. Redundant logging channels mean the same log data is sent through more than one path, so a failure in one path doesn’t stop logging. Replication to multiple media creates separate copies on different devices, protecting against a single device failure. Journaling records intent and metadata before the actual data application, giving a recoverable trail even if a write is interrupted. Commit protocols determine when a log entry is truly durable, ensuring that a write is considered complete only after it’s safely stored across mirrors or replicas. Sequence numbering enforces a strict order and helps detect gaps or out-of-order entries when resuming after failover. Integrity checks like checksums verify that log data hasn’t been corrupted in transit or storage, enabling reliable recovery. This combination prevents data loss, unlike relying on a single channel, disabling logging during failover, or using volatile memory which would be wiped by a failover event.

Fault-tolerant data logging hinges on providing multiple independent paths and ensuring durability for every write so nothing is lost during failover. Redundant logging channels mean the same log data is sent through more than one path, so a failure in one path doesn’t stop logging. Replication to multiple media creates separate copies on different devices, protecting against a single device failure. Journaling records intent and metadata before the actual data application, giving a recoverable trail even if a write is interrupted. Commit protocols determine when a log entry is truly durable, ensuring that a write is considered complete only after it’s safely stored across mirrors or replicas. Sequence numbering enforces a strict order and helps detect gaps or out-of-order entries when resuming after failover. Integrity checks like checksums verify that log data hasn’t been corrupted in transit or storage, enabling reliable recovery. This combination prevents data loss, unlike relying on a single channel, disabling logging during failover, or using volatile memory which would be wiped by a failover event.