Quick answer: Data migration is the process of moving databases, file shares and application data from one environment to another, such as from on-premises servers to Azure, AWS or Google Cloud. A safe data migration includes profiling and cleansing, choosing an online or offline transfer method, rehearsing the move, validating completeness and accuracy, and keeping a rollback path until the business signs off.
Key takeaways
- Profile and clean data before moving it; migrating bad data only moves the problem.
- Calculate transfer time from data volume and real available bandwidth early in planning.
- Use replication or continuous sync to keep cutover windows short for active databases.
- Validate with row counts, checksums and business-level checks, not just a successful job status.
- Keep the source read-only and recoverable until users have signed off.
Data is the part of a migration that cannot be rebuilt. Servers can be recreated and applications reinstalled, but a lost customer record or corrupted ledger is a real business problem. This guide explains how to move databases, file shares and application data to the cloud safely. It is part of our cloud migration services guidance.
What types of data are involved in a cloud migration?
Most small-business migrations involve four types of data, each with different methods and risks.
| Data type | Examples | Typical target | Common approach |
|---|---|---|---|
| Relational databases | SQL Server, MySQL, PostgreSQL, Oracle | Managed database service or database VM | Database migration service with replication |
| File shares | Departmental drives, home folders | SharePoint and OneDrive, Google Drive, or cloud file storage | Sync or migration tool with permissions mapping |
| Application data | Line-of-business app files, attachments | Object storage or app-specific target | Vendor tool or scripted copy |
| Archives and backups | Old project files, backup sets | Archive storage tiers | Bulk transfer or offline appliance |
How do you plan a data migration?
Plan a data migration by inventorying every source, profiling its quality and sensitivity, estimating transfer time and choosing a method for each. Planning is where most of the risk is removed.
Inventory and classify
For every data source, record its size, growth rate, owner, applications that use it, and sensitivity. Classify sensitive data such as payment, health, employee or donor information, since it affects encryption, region and access decisions.
Profile and cleanse
Data profiling looks for duplicates, missing values, inconsistent formats and orphaned records. File share profiling looks for obsolete files, very long paths, unsupported characters and broken permissions. Cleaning before migration is cheaper than cleaning after, and retiring stale data reduces both transfer time and storage cost.
Estimate transfer time
Estimate transfer time from data volume and realistic throughput, which is typically well below advertised internet speed and must be shared with normal business use. A simple rule: if the calculation shows the transfer taking more than a week or two of continuous upload, consider an offline appliance or a phased approach.
Which data migration method should you use?
Choose the method based on data volume, available bandwidth and how much downtime the business can tolerate.
| Method | How it works | Best for | Downtime |
|---|---|---|---|
| Backup and restore | Back up the source, copy the backup, restore in the cloud | Small databases with a tolerable window | Hours |
| Online replication | Initial copy plus continuous change replication until cutover | Active databases needing short cutover | Minutes |
| Incremental sync | Repeated copies of changed files until final sync | File shares | Short final sync |
| Offline appliance | Ship a physical device loaded with data | Large volumes relative to bandwidth | Plus a final online sync |
Each major cloud has native tooling:
- Databases: Azure Database Migration Service, AWS Database Migration Service (DMS), Google Cloud Database Migration Service
- Files to cloud storage: Azure Storage Mover and AzCopy, AWS DataSync, Google Storage Transfer Service
- Files to Microsoft 365: Microsoft's SharePoint Migration Tool and Migration Manager
- Offline: Azure Data Box, AWS Snowball, Google Transfer Appliance
Product names and capabilities change over time, so confirm current options during planning.
How should file shares be migrated?
File shares should be migrated with attention to structure and permissions, not just content. A file server copied without rethinking structure often becomes a cluttered SharePoint site that frustrates users.
Recommendations:
- Map each share to a destination: a team site, a shared library, OneDrive or cloud file storage
- Simplify permissions, preferring group-based access over individual grants
- Flatten deeply nested folders and shorten long paths
- Archive files untouched for several years instead of migrating them to primary storage
- Communicate with users about where files will live and how to find them
How should databases be migrated?
Databases should be migrated using a method that keeps the cutover window short and validates every table. For most business databases, a managed migration service with continuous replication is the safest approach.
Steps for a typical database migration:
- Check compatibility of the source version and features with the target service
- Create the target database with appropriate size, backup and network settings
- Migrate schema, then perform the initial data load
- Start continuous replication of changes
- Test applications against the target in a non-production configuration
- At cutover, stop writes, let replication catch up and switch connection strings
- Validate and monitor closely during the first business days
Moving from a self-managed database to a managed service is an example of replatforming in the 7 Rs, and it removes ongoing patching and backup work.
How do you validate a data migration?
Validate data at three levels: technical completeness, technical accuracy and business correctness. A migration job that reports success is not proof that data is right.
Validation checklist:
- File counts and total sizes match per folder
- Checksums match for a sample or all files
- Database row counts match for every table
- Checksums or aggregate comparisons on key tables
- Permissions tested with real user accounts
- Recent documents open correctly
- Key reports reconcile with the source, such as account balances and donation totals
- Applications pass smoke tests against migrated data
- Business owner sign-off recorded
How do you protect data during migration?
Protect data by encrypting it in transit and at rest, restricting access to migration tools, and keeping a recoverable copy of the source.
- Use encrypted connections or private connectivity for all transfers
- Grant migration accounts only the access they need, and remove them afterward
- Take a full backup of each source before cutover
- Keep sources read-only until sign-off rather than deleting them
- Apply retention policies before decommissioning
After migration, cloud-native backup should be configured and tested. Our backup and disaster recovery plan guide covers this.
What comes after migration?
Once data is in the cloud, it becomes easier to use for reporting and analytics. Many organizations follow migration with a reporting or data warehouse project; BigQuery for small business is one example of what that can look like.
How Desai InfoTech handles data migration
Desai InfoTech plans data migrations with profiling, rehearsal and multi-level validation, and keeps rollback options open until the business is satisfied. For a broader view of the process, see the cloud migration checklist, or contact us to discuss your data.
How to migrate data to the cloud: step-by-step summary
Inventory and profile
Catalog every data source, its size, owner, sensitivity and quality issues.
Choose the method
Select online replication, bulk transfer or offline appliance based on volume, bandwidth and downtime tolerance.
Cleanse and map
Remove obsolete data, fix quality issues and map source structures and permissions to the target.
Rehearse
Run a full trial migration, measure duration and validate results.
Cut over
Freeze changes, complete the final sync, switch applications and validate.
Verify and retire
Confirm business sign-off and retention requirements before retiring source data.
Frequently asked questions
How long does it take to migrate data to the cloud?
Duration depends mostly on data volume, available bandwidth and preparation. Transfer time can be estimated from volume divided by realistic throughput, which is usually well below the advertised internet speed. Planning, cleansing and rehearsal often take longer than the transfer itself. Small file shares can move in days, while multi-terabyte data sets may need weeks or an offline transfer appliance.
How do you migrate a database with minimal downtime?
Use a replication-based approach. A managed database migration service, such as Azure Database Migration Service, AWS Database Migration Service or Google Cloud Database Migration Service, copies the initial data and then continuously replicates changes while the source stays in use. At cutover, writes are stopped briefly, the final changes sync, and applications switch to the new database.
When should we use an offline data transfer device?
Offline appliances such as Azure Data Box, AWS Snowball and Google Transfer Appliance make sense when data volume is large relative to available bandwidth, meaning a network transfer would take weeks or saturate the office connection. Most small businesses with modest data volumes can migrate over the internet, but large archives, media libraries or imaging data may justify an appliance.
How do you make sure no data is lost during migration?
Validate at several levels. Compare file counts, sizes and checksums for files, and row counts and checksums for database tables. Then have business users run real checks, such as opening recent documents or reconciling report totals. Keep the source system read-only and backed up until validation is complete and the business has signed off.
Part of the Cloud Migration Services hub.