RDS
- RDS Supported DBs:
- Postgres
- MySQL
- MariaDB
- Oracle
- Microsoft SQL Server
- Aurora (AWS Proprietary database)
- RDS Features:
- Automated provisioning, OS patching
- Continuous backups and restore to specific timestamp (Point in Time Restore)!
- Monitoring dashboards
- Read replicas for improved read performance
- Multi AZ setup for DR (Disaster Recovery)
- Maintenance windows for upgrades
- Scaling capability (vertical and horizontal)
- Storage backed by EBS (gp2 or io1)
- When RDS detects you are running out of free database storage, it scales automatically
- You have to set Maximum Storage Threshold (maximum limit for DB storage)
- Automatically modify storage if:
- Free storage is less than 10% of allocated storage
- Low-storage lasts at least 5 minutes
- 6 hours have passed since last modification
- Supports for all RDS services
RDS Read Replicas
- ASYNC Replication
- Within AZ, Cross AZ or Cross Region
- Replication is ASYNC, so reads are eventually consistent
- Use cases:
- You want to run a reporting application to run some analytics
- Read replicas are used for SELECT (=read) only kind of statements
(not INSERT, UPDATE, DELETE)
- For RDS Read Replicas within the same region, you don’t pay replication fee
RDS Multi AZ (Disaster Recovery)
- SYNC replication
- One DNS name – automatic app failover to standby
- Note:The Read Replicas be setup as Multi AZ for Disaster Recovery (DR)
- No-need downtime for migrating RDS Single AZ to multi AZ
- The following happens internally:
• A snapshot is taken
• A new DB is restored from the snapshot in a new AZ
• Synchronization is established between the two databases
- Failover Conditions
- OS is undergoing software patches
- Unreachable due to loss of network connectivity
- Modified (e.g., DB instance type changed)
- Underlying storage failure
- An Availability Zone outage
- A manual failover of the DB instance was initiated using Reboot with failover