Hello and welcome back to the course. In this section, we'll be discussing RDS or relational database service. We'll start with some basic concepts. RDS is a managed relational database service that is simple to deploy, easy to scale, reliable, and cost-effective. We support a wide variety of database engines, including MySQL, MariaDB, Microsoft's SQL Server, and PostgreSQL. The service has built in high availability. The database engines are pre-tuned for performance and it is a managed service, meaning that you don't need to worry about host or database engine level configuration. It is again, fully managed, meaning that the host and operating system level configuration is handled for you by Alibaba Cloud. It comes with fully-managed storage as well, you don't need to worry about how the database storage tier works, that's handled by us. Databases support up to 20,000 IOPS and two terabytes of storage for each RDS instance that you create, and you can upgrade memory and disk space according to your needs. Again, as a managed service, this is grab and go. There's built-in operations, backup, monitoring, and security tools and of course, availability in the 3-node HA version of the service reaches up to 99.9 percent with automatic failover. There are some trade-offs here. If you're building your own database, the traditional way, you have to prepare the hardware, install the OS, install your database software, configure the database software, and then do performance tuning and tweaking. That can take 3-5 hours. Actually I think that's an optimistic estimate, this is probably 1-2 days worth of work. On the other hand, if you're using Alibaba Cloud's RDS, you can have a database up and running in just 10 or 15 minutes. You choose your engine, you choose your database instance specification, which is how much memory, how many CPU cores, and how much storage you want, and then that's it. The database is ready to run. The only reason you would choose a traditional database is if you have some very specific, unique need for a particular feature that maybe we don't support or that maybe is new or you're using a database engine that won't run on top of the RDS service. Otherwise, RDS is a sovereign choice. RDS, like our other services, runs on top of Apsara. It runs on top of the Apsara platform and it depends on Apsara services like the distributed file system, Pangu, in order to run properly. Unlike ECS, RDS is a PaaS service, meaning that in addition to servers, storage, networking, and virtualization, Alibaba Cloud also manages the operating system, middleware, and database runtime. You only need to worry about setting up databases and creating database users. That's it. You don't have to worry about actually tuning MySQL or PostgreSQL, or patching or updating your operating system. That's all handled for you by us. Again, just to compare Infrastructure as a Service and Platform as a Service, you can see that with ECS, the operating system is also your responsibility. You have to make sure that it's patched and updated and working properly. But for RDS, you really only need to worry about the data and application layer at the very top of the stack there in blue. The architecture for RDS is fairly complex. Essentially, we have a suite of security services sitting in front of a cluster of RDS database nodes. Those database nodes are accessible on the common ports that you would normally use to access a relational database. For instance, for MySQL, that would be port 3306. Those database nodes are then connected to our high availability control system which checks for failures and our backup system, online migration systems to handle failures, and task schedulers and monitoring systems as well. Of course, all of this is transparent to you as the user. That's all for this section. In the next section, we'll take a look at different RDS instance types.
