Overview of Database Migration Service

Database Migration Service makes it easier for you to migrate your data to Google Cloud. Database Migration Service helps you lift and shift your MySQL and PostgreSQL workloads into Cloud SQL. Database Migration Service streamlines networking workflow, manages the initial snapshot and ongoing replication, and provides a status of the migration operation.

For businesses that are migrating their workloads to the cloud, there can be considerable friction in moving their on-premises and other cloud-based databases to Google Cloud. This can slow their ability to take advantage of the capabilities that Google Cloud has to offer.

Migration concepts

Migration is a process whereby data and metadata is moved from a source database to a destination database. After the migration is completed, the destination database becomes the primary database, dependent applications should read and write to it, and the source database can be shut down.

Continuous (sometimes referred to as ongoing or online) migration is a continuous flow of changes from your source to your destination that follows an initial full dump and load. In the case of a migration, when the time comes to switch to use the destination for reads and writes, promote the migration. As a result, the destination Cloud SQL instance is disconnected from the source, and is promoted from a replica instance to a primary instance. Doing the promotion when the source and destination are in sync gives you minimal downtime.

Behind the scenes

The migration to Cloud SQL leverages the primary-replica relationships enabled by native tooling for MySQL and PostgreSQL. That means:

  • When setting up a migration, a replica instance appears in the Cloud SQL instance list, attached to the source that was set up.

  • When performing a promotion, the replica disconnects from the source and is modified to read/write mode. It can then serve as a primary for other replicas, and other options can be changed such as the HA setting.

Use cases

The migration capabilities of Database Migration Service enable a variety of use cases:

  • Lift and shift migration to a managed service

    As part of an organization's move to Google Cloud, there's an opportunity to move from VM-based self-hosted databases to managed database cloud services. This allows teams to get out of the business of managing infrastructure, and enjoy the high availability, disaster recovery, and performance of running databases on managed services.

  • Multi-cloud continuous replication

    Much like the read replicas across regions, if data exists in another cloud provider, a migration job can be set up which continuously replicates the database into Google Cloud for multi-cloud read-availability. Database Migration Service doesn't support a dual-write scenario, that is writing to and reading from both the source and destination.

Experience elements

There are two main elements that comprise Database Migration Service:

  • Connection profiles represent connectivity information to the specific source that will be used in a migration job.

  • Migration jobs represent a source connection profile and destination Cloud SQL instance pair, along with migration-specific settings.