11 - RDS Multi-AZ and Read Replicas Flashcards
1
Q
Multi-AZ RDS
A
Multi-AZ RDS
- Multi-AZ RDS is for disaster recovery only.
- It is not used for improving performance.
- To improve performance you need read-replicas
2
Q
Read Replicas
A
Read Replicas
- Used for scaling, not disaster recovery
- Must have automatic backups turned on in order to deploy a read replica
- You can have up to 5 read replica copies of any database
- You can read replicas of read replicas (but long latency)
- Each read replica will have its own DNS end point
- You can have read replicas that have multi-AZ enabled
- You can crate read replicas of multi-AZ source databases
- Read replicas can be promoted to their own databases (this breaks the read replication)
- You can have a read replication in another region (for MySQL and MariaDB)
3
Q
DB Backups - Overview
2 types - Automated Backups & Database Snapshots
A
DB Backups - 2 types - Automated Backups & Database Snapshots
Automated Backups
- Can recover database to any point in time, within a “retention period”.
- The period can be between 1 - 35 days.
- This is a full daily snapshot, and will also store transaction logs through out the day.
- When recover will first pull the most recent daily backup, and then apply all relevant transaction logs to that day.
- This allows for point in time recovery down to a second, with a retention period.
- They are enabled by default.
- Backup data stored in S3, and you get free storage equal to the size of your database.
- Backups are taken within a defined window
- During back up window, storage I/O may be suspended while data is being backed up which could cause elevated latency
Database Snapshots
- Snapshots are done manually (user initiated)
- Snapshots are stored even after you delete the original RDS instance (unlike automated backups which are deleted if the database is deleted)