AWS : Relational Database Service (RDS) - Basics Part 2

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How do I ensure database high availability?

• Multi-AZ provides enterprise-grade fault-tolerance solution for production databases
    • Automatic failover
    • Synchronous replication
    • Inexpensive and enabled with one click

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What happens during a Multi-AZ failover? How long does it take?

• Each host manages set of Amazon EBS volumes with a full copy of the data
• Instances are monitored by an external observer to maintain consensus over quorum
• Failover initiated by automation or through the Amazon RDS API
• Redirection to the new primary instance is provided through DNS

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Why would I use Read Replicas?

• Relieve pressure on your source database with additional read capacity
• Bring data close to your applications in different regions
• Promote a Read Replica to a master for faster recovery in the event of disaster
• Upgrade a Read Replica to a new engine version•Supported for MySQL, MariaDB, and PostgreSQL

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When should I use Multi-AZ ?

 • Synchronous replication—highly durable
 • Only primary instance is active at any point in time
 • Backups can be taken from secondary
 • Always in two Availability Zones within a Region•Database engine version upgrades happen on primary
 • Automatic failover when a problem is detected

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When should I use Read Replicas ?

 • Asynchronous replication—highly scalable
 • All replicas are active and can be used for read scaling
 • No backups configured by default•Can be within an Availability Zone, cross-AZ, or cross-region
 • Database engine version upgrades independently from source instance
 • Can be manually promoted to a standalone databaseRead ReplicasMulti-AZ

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How does Amazon RDS manage backups?

• Two options –automated backups and manual snapshots
• Amazon RDS backups leverage Amazon EBS snapshots stored in Amazon S3
• Transaction logs are stored every 5 minutes in Amazon S3 to support point-in-time recovery (PITR)
• No performance penalty for backups
• Snapshots can be copied across regions or shared with other accounts

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When should I use automated backups?

• Specify backup retention window per instance (7-day default)
• Kept until outside of window (35-day maximum) or instance is deleted
• Supports PITR
• Good for disaster recovery

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When should I use snapshots?

• Manually created through AWS console, AWS CLI, or Amazon RDS API
• Kept until you delete them
• Restores to saved snapshot
• Use for checkpoint before making large changes, non-production/test environments, final copy before deleting a databaseManual snapshots

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How do I restore a backup? Why does it take so long?

- Restoring creates an entirely new database instance
    • Define the instance configuration just like a new instance
    • Will get the default parameter, security, and option groups

- New volumes are hydrated from Amazon S3
    • While the volume is usable immediately, full performance requires the volume to warm up until fully instantiated
    • Migrate to a DB instance class with high I/O capacity
    • Maximize I/O during restore process

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