Design and Implementation of Database Backup and Recovery Strategies

Design and Implementation of Database Backup and Recovery Strategies

Problem Description
Database backup and recovery are core mechanisms for ensuring data security and business continuity. The interviewer aims to assess your ability to systematically explain backup types (physical/logical, full/incremental/differential), recovery models (simple/full/bulk-logged), and how to design backup and recovery solutions that balance efficiency and reliability. Next, I will break down the key knowledge points step by step.

1. Backup Type Classification and Characteristics
Backups can be categorized from two dimensions:

  • Physical Backup vs. Logical Backup

    • Physical Backup: Directly copies database files (e.g., data files, log files).
      • Advantages: Fast recovery speed, high compatibility.
      • Disadvantages: Storage engine dependent, difficult to migrate across platforms.
      • Examples: MySQL's xtrabackup, Oracle's RMAN.
    • Logical Backup: Exports SQL statements or data records (e.g., mysqldump).
      • Advantages: High readability, compatible with different versions or engines.
      • Disadvantages: Slow recovery (requires replaying SQL), potential loss of precision (e.g., floating-point numbers).

  • Full Backup vs. Incremental Backup vs. Differential Backup

    • Full Backup: Completely backs up all data.
      • Applicable scenarios: Small data volume or strict Recovery Time Objective (RTO).
    • Incremental Backup: Only backs up data changed since the last backup (relies on logs or snapshots).
      • Characteristics: Fast backup, but recovery requires sequentially merging all incremental backups.
    • Differential Backup: Backs up all changes since the last full backup.
      • Characteristics: Recovery only requires the full backup + the latest differential backup, balancing efficiency and complexity.

2. Recovery Models and Log Management
The database recovery model determines the granularity of log recording and affects backup strategies:

  • Simple Recovery Model: Log space is automatically reused, does not support Point-in-Time Recovery (PITR).
  • Full Recovery Model: Logs are fully recorded, supports PITR, but requires regular log backups.
  • Bulk-Logged Recovery Model: Minimizes logging during bulk operations, balancing performance and recoverability.
    Key Point: Choosing a model requires balancing data importance and log storage costs. For example, financial systems need to use the full recovery model.

3. Backup Strategy Design Principles
Design must combine business requirements and resource constraints:

  • RTO (Recovery Time Objective): Specifies the time required for recovery after a system interruption.
    • Short RTO: Requires physical backup + hot standby mechanisms (e.g., master-slave switching).
  • RPO (Recovery Point Objective): Defines the allowable amount of data loss.
    • Low RPO: Requires frequent log backups (e.g., every 5 minutes).
  • Typical Solution Examples:
    • Scenario 1: E-commerce database (large data volume, tolerates minute-level data loss).
      • Strategy: Weekly full backup (physical) + daily incremental backup + hourly log backup.
    • Scenario 2: Development/test environment (data can be rebuilt).
      • Strategy: Daily logical backup (saves space).

4. Recovery Process and Fault Handling
Recovery must follow strict steps:

  1. Identify Fault Type:
    • Data file corruption → Restore from physical backup.
    • Accidental data deletion → Use log backup for PITR.
  2. Recovery Order:
    • Restore the latest full backup.
    • Apply differential/incremental backups in chronological order.
    • Replay log backups up to the moment before the failure.
  3. Verification Mechanisms:
    • Perform data consistency checks after recovery (e.g., MySQL's mysqlcheck).
    • Simulate fault drills to ensure RTO/RPO compliance.

5. Advanced Techniques and Considerations

  • Backup Encryption and Compression: Prevents data leakage, reduces storage pressure (e.g., using AES-256 encryption).
  • Cross-Region Disaster Recovery: Stores backups in different regions (e.g., AWS S3 cross-region replication).
  • Monitoring and Alerts: Monitors backup task status, storage space, and backup duration.

By following these steps, you can flexibly combine backup types and recovery models based on actual scenarios to form a reliable data protection solution.