Choosing between AWS RDS MySQL and Self Managed MySQL EC2

The Amazon Web Service (AWS) products AWS EC2 and AWS RDS comes with sophisticated technology features and capabilities that serve the needs for Web based computing and storage efficiently. When coming to the decision making process for selecting between AWS RDS and the self managed AWS ECS or any independent MySQL DBaaS for your MySQL database needs, there are some prominent factors to consider. These factors are crucial and affect the operational and economic aspects of your database deployment. This article provides a comprehensive overview of both products to help you understand the distinction between them for making a suitable and cost-effective decision.
Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides scalable cloud computing facilities. You can select either a pre-configured instance optimized for your application needs or first deploy an instance and configure it through provisioning and scale up/down facilities. The EC2 packages are organized according to the level of optimization and resource allocation done in terms of CPUs, Memory, Storage, etc.
Its advantages are:
1. Pay per provisioning.
2. Quick scale up/down capabilities.
3. Self managed with root access and allows configuration of CPU, memory, storage etc.
4. Rapid commissioning of multiple server instances.
5. Choice to select instance types and OS (Linux and Windows).
6. Availability of pre-configured instances.
7. Flexibility to choose instance location.
8. Elastic IP addresses.
Amazon Relational Database Service (RDS) is a managed web service that assists in setting up a relational database in cloud. Its advantages are:
1. Resource scaling.
2. Automated database administration for hardware provisioning, database setup, patching, upgrades, backups, etc.
3. Automatic failure detection and recovery.
4. Flexibility to schedule and perform backups and restore operations.
6. Read scaling through Read Replicas.
7. Availability of AWS IWM (Identity and Access Management) and network isolation through Amazon Virtual Private Cloud (VPC) to enhance security.
8. On-demand pricing.
9. High availability with provisioning of Multi-AZ DB instance deployments with synchronized standby replicas on different Availability Zones for automatic failover and recovery.
Amazon RDS is implemented by using DB instances – an isolated database environment in the cloud and can contain multiple databases. A DB instance can be created and modified by using the AWS CLI, the AWS API or the AWS management console. Currently the Amazon RDS supports the DB engines: Amazon Aurora, PostgreSQL, MySQL, MariaDB, Oracle and SQL Server.
Amazon MySQL RDS
It is the MySQL based DB instance deployments in the cloud. As like other types of DB engines, MySQL RDS also offers advantages like high availability, automated DB administration, backup and recovery, provisioned storage and IOPS with scaling, read replicas on different AWS regions for load balancing and automatic failover, isolation and security, Multi-AZ instances with synchronous standby replicas on separate Availability Zones for failover and backups, etc.
Limitations with MySQL RDS
1. Storage is charged per provisioning, not according to consumption. Once storage is allocated, it cannot be returned without rebuilding the instance from scratch or a logical backup restore.
2. Access to the Operating System and Shell Access is denied. So tasks that need to be run from an OS access cannot not be done.
3. MySQL user accounts with SUPER privilege are not allowed. Operations that need this privilege like setting of some system variables, replication configuration and operations, binary log management, InnoDB key rotation etc. cannot be performed. These can only be achieved through RDS stored routines and RDS parameter groups.
4. There is no slow query log, instead need to use RDS provided mechanism for logging slow queries.
5. There is no multi-master replication in RDS. For Single Zone instances there is one master and multiple read replicas with asynchronous replication and no failover. This means that the replication is not fault proof and may cause data loss. Multi-AZ instances come with additional cost and have a primary instance and standby secondary instance at another zone. Though they use synchronous replication, the secondary database is in-active and couldn’t be used until the failover. Then the secondary becomes the primary.
6. Scale up or down is automatic but have downtime due to switchover time.
7. Replicating from AWS RDS to another cloud provider is not supported.
8. Does not support all available MySQL replication options like multi-master, multi-source, tree replication etc.
Cost Comparison 
Base Cost calculation for the m4.large setup (2 X vCPU, 8 GB Memory) as on September 8, 2017 for 1 month of usage for EC2, Single Zone RDS and Multi-AZ RDS
EC2 m4.large
$0.1 per Hour X 24 hours X 30 days = $72
Single Zone RDS db.m4.large
$0.175 per Hour X 24 hours X 30 days = $126
Multi-AZ RDS (Multi Zone) db.m4.large
$0.350 per Hour X 24 hours X 30 days = $252
We can see that base monthly cost (without adding backup storage and bandwidth) for RDS is almost double with EC2 for the same configuration. When it comes to Multi-AZ RDS, it becomes double than Single Zone RDS.
The Conclusion
AWS RDS is a fully managed solution and you have little to do in terms of frequent and daily DBA tasks. So you are free to focus on the application side and its connectivity and interface to the already running database. It is a good choice for critical business implementations where little customizations are needed and scalability is the main constraint.
AWS EC2 on the other side demands good effort in configuring and managing your DB deployment. But the flexibility is that, if you have reasonable expertise with DBA tasks, you can implement a tailored DB setup with your choice of configuration, optimization and other enhancements like specialized scripts for carrying out custom tasks etc. Along with the cost effectiveness, EC2 is suitable if you need multiple RDS instances or your MySQL server has a variety of plugins needed. So you can go for EC2, if you need to have the flexibility of setting up an adaptive DB implementation that scale and evolve with your applications.

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