Moving a database to the cloud is one of the most consequential infrastructure decisions an engineering team can make. Choosing the wrong migration service risks data loss, extended downtime, and cost overruns. This article compares the primary managed database migration offerings from five major cloud providers: AWS, Google Cloud, Microsoft Azure, IBM Cloud, and Alibaba Cloud.
What Is Database Migration?
Database migration is the process of moving data, applications, and associated workloads from one platform or location to another. In a cloud context this typically means moving from on-premises infrastructure — or from a competing cloud — to a target cloud environment, with the goals of reducing operational overhead, improving scalability, and controlling cost.
Why Migrate a Database to the Cloud?
Common motivations for cloud database migration include:
- Cost optimisation — pay-as-you-go billing replaces large upfront hardware investment.
- Scalability — cloud-managed databases can scale vertically or horizontally on demand.
- Data availability and durability — managed services typically offer multi-AZ replication and automated backups.
- Reduced manual effort — patching, upgrades, and failover are handled by the provider.
- Data integrity — purpose-built migration tools include checksums and validation to verify data fidelity.
- Improved operational efficiency — freeing DBA time from routine maintenance allows focus on higher-value work.
Cloud Database Migration Services Compared
1. AWS Database Migration Service (AWS DMS)
AWS Database Migration Service (DMS) is a fully managed service that supports migration of relational databases, data warehouses, NoSQL databases, and other data stores. It is one of the most mature offerings in this space and supports a broad range of source and target engine combinations.
Key capabilities
- Homogeneous migrations — same engine on source and target (e.g., Oracle to Oracle).
- Heterogeneous migrations — different engines (e.g., Oracle to Amazon Aurora). The AWS Schema Conversion Tool (SCT) is used alongside DMS to convert the schema and stored code.
- Minimal downtime — the source database remains fully operational during migration; DMS uses ongoing replication to keep the target in sync until cutover.
- Flexible topology — supports cloud-to-cloud, on-premises-to-cloud, and hybrid (on-premises-to-cloud combined) scenarios.
Pricing
AWS offers a free tier for migrations to Amazon Aurora, Amazon Redshift, or Amazon DynamoDB for the first six months. For other migrations, pricing is based on the replication instance compute resources consumed. Additional charges apply for log storage beyond the included allowance. Current pricing is published on the AWS DMS pricing page.
2. Google Cloud Data Transfer Services
Rather than a single monolithic service, Google Cloud offers a family of data transfer products, each optimised for a specific scenario.
| Service | Best suited for |
|---|---|
| Online Transfer | Moving data to Cloud Storage over a standard network connection. |
| Cloud Storage Transfer Service | Cloud-to-cloud transfers, including from other providers (e.g., Amazon S3) and bucket-to-bucket moves within Google Cloud Storage. |
| Transfer Appliance | Large-scale offline transfers; available in 100 TB and 480 TB physical appliance models for environments where network transfer is impractical. |
| BigQuery Data Transfer Service | Scheduled, automated ingestion from SaaS applications and other Google services into BigQuery. |
Cloud Storage Transfer Service also exposes a JSON API, allowing teams to script and automate transfers in the language of their choice. This makes it well-suited to DevOps pipelines where migration tasks need to be triggered programmatically.
Pricing
Google Cloud charges for storage capacity used, network egress, API operations, and (where applicable) early deletion fees. Costs vary by storage class and region. Current rates are on the Google Cloud Storage pricing page.
3. Azure Database Migration Service (Azure DMS)
Azure Database Migration Service is a fully managed service designed to handle migrations from multiple source engines to Azure-managed database services. It is closely integrated with the Azure portal and the Data Migration Assistant (DMA) tool.
Supported source engines
- SQL Server
- PostgreSQL
- MySQL
- MongoDB
Supported target engines
- Azure SQL Database
- Azure SQL Managed Instance
- Azure Database for PostgreSQL
- Azure Database for MySQL
- Azure Cosmos DB (MongoDB API)
Migration modes
Azure DMS supports two migration modes:
- Offline migration — the database is taken offline at the start of the migration. Simpler to orchestrate but involves planned downtime. Available on the Standard tier at no charge.
- Online migration — continuous replication keeps the source database live during the migration, with a brief cutover window. Recommended for production workloads with tight availability requirements. Requires the Premium tier.
The Data Migration Assistant (DMA) can be run before migration to generate compatibility assessment reports and flag breaking changes or deprecated features, helping teams address issues before cutover.
Pricing
- Standard tier — free; supports offline migrations; available in 1, 2, and 4 vCore configurations.
- Premium tier — billed at a predictable hourly rate per provisioned vCore; supports online migrations. Microsoft has offered a free period for Premium 4-vCore instances for new migrations (verify current promotion on the Azure pricing page).
4. IBM Lift
IBM Lift is a migration utility designed specifically to move databases from on-premises data centers to IBM Cloud. The tool orchestrates the full migration pipeline — extraction from the source, secure transfer over the network, and loading into the target.
Key capabilities
- Live source database — IBM Lift captures incremental changes made to the source database during the migration and replays them to the target, keeping the source operational and minimising downtime.
- Encrypted transfer — data is transmitted over a 256-bit encrypted connection end-to-end, protecting sensitive data in transit.
- Controlled migration steps — teams retain visibility and control over each stage: extract, transfer, and load.
Pricing
IBM Lift has been available at no charge. Confirm current availability and any attached IBM Cloud service costs on the IBM Cloud catalogue.
5. Alibaba Cloud Data Transmission Service (DTS)
Alibaba Cloud’s Data Transmission Service (DTS) is a managed migration and replication service that supports a wide range of database types, including relational databases, NoSQL stores, and OLAP systems.
Key capabilities
- Homogeneous and heterogeneous migrations — supports same-engine moves (e.g., MySQL to MySQL) and cross-engine moves (e.g., Oracle to MySQL).
- Flexible source and target topology — supports on-premises to RDS, ECS-hosted databases to RDS, RDS to ECS, and RDS to RDS migrations.
- Continuous replication — DTS replicates changes from the source to the target in real time during migration, keeping the source database available and reducing the risk of data loss at cutover.
- High availability — the continuous change capture mechanism also serves as a foundation for ongoing replication after initial migration if needed.
Pricing
Alibaba Cloud DTS pricing is based on the instance specification selected for the migration task and the duration of use. Current pricing is available in the Alibaba Cloud console and documentation.
Side-by-Side Summary
| Provider | Service name | Homogeneous | Heterogeneous | Online (minimal downtime) | Free tier |
|---|---|---|---|---|---|
| AWS | AWS DMS | Yes | Yes (+ SCT) | Yes | 6 months to Aurora/Redshift/DynamoDB |
| Google Cloud | Cloud Data Transfer family | Yes | Varies by service | Yes (Transfer Service) | Some operations free; storage charged |
| Azure | Azure DMS | Yes | Yes | Yes (Premium tier) | Standard tier free; Premium trial available |
| IBM | IBM Lift | Yes | Limited | Yes | Free |
| Alibaba Cloud | DTS | Yes | Yes | Yes | Varies by task type |
Choosing the Right Service
The right migration service depends on where your data currently lives, where it needs to go, and what downtime budget you have. A few practical guidelines:
- If your target is an AWS-managed database, AWS DMS is the natural choice, especially given the free migration period for Aurora, Redshift, and DynamoDB.
- If you need to ingest large volumes of SaaS data into a data warehouse, BigQuery Data Transfer Service offers native scheduling and automation.
- If you are migrating to Azure and need pre-migration compatibility assessment, the Data Migration Assistant paired with Azure DMS provides a structured, guided process.
- For IBM Cloud destinations with a zero-cost requirement, IBM Lift is worth evaluating first.
- For mixed Alibaba Cloud environments involving RDS or ECS instances, Alibaba Cloud DTS provides the tightest integration with the platform.
Always run a proof-of-concept migration on a non-production copy of your data before committing to a production cutover, regardless of which service you choose.