Restore Points

Log After Backup

Writes after the snapshot are recorded as ordered log entries.

highlighted = computed this step

Log after backup

After the snapshot, each write is recorded in a small ordered log.

ordered write log\text{ordered write log}

Show the log

The log has 3 records. The chosen target is position 1.

records=3\text{records}=3

Backup and restore-point examples are tiny finite replay models; cloud products, backup strategy, RPO/RTO, encryption, compliance, performance, and runbooks are out of scope.

Log after backup: backup snapshotitemvalueA10B20 log after backuppositemvalue1A112B253A13 restore point factsfactvaluetarget1appliedCount1skippedCount2changedCount1targetIsBackupnotargetInLogyes applied log recordspositemvalue1A11 skipped log recordspositemvalue2B253A13 restored stateitemvalueA11B20 changed itemsitembeforeafterA1011

Use positions, not guesses

The integer positions decide what can be replayed. The lesson does not infer hidden time or product behavior.

position decides\text{position decides}

Summary

A log record after the backup is only useful when the restore point includes it.

after backup\text{after backup}