Exploring AWS !!

Day 38:

Amazon RDS:

Check out Day 37 for Overview and advantages of RDS over deploying database on EC2.

https://dev.to/rksalo88/learning-aws-day-by-day-day-37-amazon-rds-redshift-and-aurora-overview-3g0d

RDS Backups:

• Backups are automatically enabled.
• Automated backups
• Daily full backup of database (during maintenance windows)
• Transaction logs are backed up by RDS every 5 minutes
• ability to restore at any point in time (from oldest to 5 mins ago)
• 7 days retention (increased to 35 days)
• Database snapshots: Manually triggered by user Retention of backup for as long as you want.

RDS — Storage Autoscaling:

• Helps increase storage on RDS database instance dynamically
• When RDS detects you are running out of free database storage, it scales automatically.
• Avoid manually scaling database storage
• You have to set the maximum storage threshold (max limit for database storage)
• Automatically modify storage if: Free storage is less than 10% of allocated storage Low storage lasts at least 5 mins 6 hours have been passed since last modification
• Useful for apps with unpredictable workloads
• Supports all RDS database engines (MariaDB, MySQL, PostgreSQL, SQL server, Oracle)

RDS Read Replicas for read scalability:

• can create upto 5 replicas
• within Az, cross Az or cross region
• Replication is Asynchronous, so reads are eventually consistent
• replication can be promoted to own database
• Application must update connection string to leverage read replicas.

Use Cases:
You have a production application that is taking on normal load.
You want to run a reporting application for running some analytics.
So, you create a read replica to run new workload there.
The production application is unaffected.
Read replicas are used for SELECT (=read) only kinds of statements (not INSERT, UPDATE or DELETE)

RDS Read Replicas — Network Cost:
There’s some network cost when data goes from one Az to another Az.
For RDS Read Replicas within same region, you don’t pay fees.

RDS Multi-AZ (Disaster Recovery):

• SYNC Replication
• One DNS name — automatic app failover to standby
• Increase availability
• Failover in case of loss of AZ, loss of network, instance or storage failure
• No manual intervention in applications
• Not used for scaling Note: Read replicas can be setup as Multi-AZ for Disaster Recovery(DR).

RDS from Single AZ to Multi-AZ:

• Zero downtime operation (no need to stop database)
• Just click “modify” for database
• Following happens internally: A snapshot is taken A new database is restored from snapshot in a new AZ Synchronization is established between 2 databases