# AWS 共學 Week3: RDS, AuroraDB, ElastiCache
Host: Eric Chang
###### tags: AWS, ElastiCache, AuroraDB
>目標: 每個 Part 需要做一些基本介紹，然後給出一個 Demo，讓大家了解對應服務使用上的細節
## Part1: RDS
成員: AC, Gin
For relation database:
Postgres, MySQL, MariaDB, Oracle, Microsoft SQL Server, Aurora
### RDS vs DB on EC2
* 免處理os方面的事情
* 自動幫你備份
* Read replicas (讀寫分離)
* 跨AZs for HA
* 自行設定維護時間
* Auto Scaling: set the Max storage value.
* EBS
* No SSH
### Read Replicas
* 只能SELECT
* 最多5個
* 同AZ,跨AZ,跨區
* ASYNC (每隔5分鐘)
* 如果RR變動 需手動更新連線資訊
* 數據傳輸
AWS 跨AZ \$\$
RDS 跨AZ Free
RDS 跨區 \$\$
### Multi-AZ (RDS AZs)
* SYNC
* One DNS (自動更新連線資訊)
* 自動災難轉移
* Not for scaling, No one can access
* Read replicas can be Standby
### RDS AZ -> AZs
* No downtime
* Just click on modify
* 內部流程
1.snapshot
2.restore from snapshot
3.build SYNC
### RDS Custom
* Ec2 + OS + Oracle/MS-SQL
* SSH
### Aurora
* AWS 優化過 (更快更大) ~~工商時間~~
* MYSQL / Postgres
* 15 replicas vs MySQL 5 replicas
* Cost more, but efficient
* HA (瞬間故障轉移)
* Auto-scling ~128T
* 6 copies in 3 AZs
* Only ONE (Master) for read/write
* the others for read/restore
* Writer/Reader endpointer (load balancing) for connection level
* Restore at ANY time vs RDS at each 5-min
## Part2: AuroraDB
成員: 大Leo, Rick, Saker
補充
- [複製 Amazon Aurora 資料庫叢集的一個磁碟區
](https://docs.aws.amazon.com/zh_tw/AmazonRDS/latest/AuroraUserGuide/Aurora.Managing.Clone.html)
## Part3: ElastiCache
成員: Larry, Bear