Backups and Disaster Recovery Strategy – MySQL
Category: Administration → MySQL
Applies To: MySQL 8.x
Issues Summary:
A robust backup and disaster recovery (DR) strategy is paramount for any MySQL database production. It ensures data protection against various failures (hardware, software, human error, natural disaster), minimizes data loss (RPO - Recovery Point Objective), and reduces downtime (RTO - Recovery Time Objective). This document outlines key concepts, tools, and strategic components for establishing an effective MySQL backup and DR plan.
Key Concept and Tools:
Recovery Point Objective (RPO): The maximum tolerable amount of data loss, measured in time (e.g., 1 hour of data). Determined by backup frequency and binary log retention.
Recovery Time Objective (RTO): The maximum tolerable amount of downtime, measured in time (e.g., 4 hours of unavailability). Influenced by restoration speed and failover mechanisms.
Backup Types:
Full Backup: A complete copy of all data at a specific point in time.
Incremental Backup: Captures only changes since the last full or incremental backup. Faster but more complex restoration.
Differential Backup: Captures changes since the last full backup. Faster to restore than incremental, but larger than incremental backups.
Backup Methods:
Logical Backups (e.g., mysqldump):
Description: Exports data as SQL statements. Human-readable and portable across versions/architectures.
Pros: Easy to use, great for schema-only backups, small datasets, or specific tables.
Cons: Slow for large databases, takes longer to restore, and can be resource-intensive during backup.
Tools: mysqldump (built-in).
mysqldump -u [uname] -p db_name > db_backup.sql
Physical Backups (e.g., Percona XtraBackup):
Description: Copies raw data files (InnoDB tablespaces, logs) directly. Faster for large databases.
Pros: Very fast for large databases, hot backups (no read/write locks), faster restoration.
Cons: Less portable, requires specific tools, and can be more complex to manage.
Tools: Percona XtraBackup (open-source, highly recommended), MySQL Enterprise Backup (commercial).
Point-in-Time Recovery (PITR):
Description: The ability to restore a database to any specific point in time (e.g., just before an accidental DROP TABLE). Achieved by applying binary logs (binlogs) from a full/incremental backup onwards.
Requirement: MySQL Binary Logging must be enabled (log_bin in my.cnf).
Replication:
Description: Asynchronously or semi-synchronously copies data changes from a master to one or more slave servers.
Purpose: Primarily for High Availability (HA), read scaling, and also forms the backbone of many DR strategies.
Types:
Asynchronous Replication: Default. Master doesn't wait for slave acknowledgment. Low latency, but potential for data loss on master crash.
Semi-synchronous Replication: Master waits for at least one slave to acknowledge receipt of changes. Better durability, slightly higher latency.
MySQL Group Replication / InnoDB Cluster: Multi-master, high-consistency solution for HA and read scaling, providing automatic failover.
Backup and DR Strategy Components
Define RPO and RTO:
Crucially, define these based on business requirements. This drives decisions on backup frequency, type (logical vs. physical), and replication choice.
Backup Schedule and Retention Policy:
Full Backups: Weekly or bi-weekly.
Incremental/Differential Backups: Daily, hourly, or even more frequently for critical data.
Binary Logs: Continuously collected and safely stored. Their retention duration dictates your maximum RPO.
Retention: How long backups are kept (e.g., 1 month, 3 months, 1 year).
Backup Verification:
Crucial Step: Backups are useless if they cannot be restored.
Method: Regularly perform test restores of your backups to a non-production environment. Validate data integrity and application functionality.
Offsite Storage for Backups:
Store backup copies in a separate geographical location or cloud region from your primary data center. This protects against site-wide disasters.
Methods: Cloud storage (S3, GCS, Azure Blob), dedicated offsite data centers.
Replication Setup for HA and DR:
High Availability (HA): Deploy primary (master) and secondary (slave/standby) servers. Use automatic failover tools (e.g., Orchestrator, MHA, native Group Replication) to reduce RTO.
Disaster Recovery (DR): Set up a slave in a separate data center/cloud region. This acts as your DR site. In case of primary region failure, this slave can be promoted.
Comprehensive Disaster Recovery Plan (DRP):
Documentation: A detailed, step-by-step document outlining procedures for:
Detecting a disaster.
Initiating failover to the DR site (if replication is used).
Restoring from backups (if replication is not sufficient or data corruption occurred).
Failback to the primary site after recovery.
Regular Testing (DR Drills): Periodically execute the DRP in a simulated environment to identify gaps, refine procedures, and ensure personnel are familiar with the process. This is the only way to confirm RTO/RPO.
Security for Backups:
Encryption: Encrypt backup data, especially when stored offsite or in the cloud.
Access Control: Implement strict access controls (least privilege) for backup storage and the tools used to manage them.
Monitoring:
Monitor backup job status (success/failure).
Monitor replication lag to ensure the DR slave is up-to-date.
Monitor disk space on backup targets.
Additional Notes:
Workload Impact: The choice of backup method (logical vs. physical) and replication type depends heavily on your database size, write volume, and RTO/RPO requirements. Large, high-traffic databases benefit significantly from physical backups and semi-synchronous/group replication.
Managed Services: For cloud deployments (AWS RDS, Azure Database for MySQL, Google Cloud SQL), the cloud provider often handles physical backups, PITR, and replication, simplifying the DR strategy significantly. Understand their service level agreements (SLAs) for RPO/RTO.
Continuous Improvement: Regularly review and update your backup and DR strategy as your data volume grows, business requirements change, and new tools/technologies emerge.
Storage Infrastructure: Ensure the backup storage infrastructure is robust, scalable, and separate from your primary database storage.