Database Migration Downtime Calculator
Estimate and Minimize Downtime for Database Migrations
Plan smooth database migrations by predicting expected downtime, minimizing business impact, and optimizing migration strategies. This calculator is perfect for DBAs, devs, and SREs managing production data moves.
Database Migration Downtime Calculator
Estimate and minimize downtime for database migrations by simulating different strategies.
About This Tool
The Database Migration Downtime Calculator is a critical planning tool for Site Reliability Engineers (SREs), Database Administrators (DBAs), and developers. Migrating a production database—whether for a version upgrade, a move to the cloud, or a switch to a different database engine—is a high-stakes operation where downtime can directly impact revenue and customer trust. This tool helps quantify the risks by providing a data-driven estimate of the expected downtime. By inputting key variables like data volume, network throughput, and the chosen migration strategy (from a full offline dump/restore to a more sophisticated logical replication cutover), it simulates the migration process and calculates the time your application will be unavailable. It allows teams to compare the trade-offs of different methods, communicate realistic maintenance windows to stakeholders, and justify the engineering effort required for more complex, near-zero-downtime migration techniques.
How to Use This Tool
- Enter the total size of your database in Gigabytes (GB).
- Input the available network speed between your source and target databases in Megabytes per second (MB/s).
- Select your migration method: "Offline Dump & Restore" for full downtime, or "Replication & Cutover" for a low-downtime approach.
- If using replication, estimate the final "Replication Lag" in seconds that you need to sync during the cutover.
- Click "Estimate Downtime" to see the results.
- The tool will provide an estimated time your application will be down, along with a risk assessment and tips for reducing that time.
In-Depth Guide
Migration Method 1: The Offline Dump and Restore
This is the simplest and most traditional migration method. It involves three steps: 1. Take the source database offline (begin downtime). 2. Create a full backup (a "dump") of the data. 3. Transfer the backup file to the target server and "restore" it. The total downtime is the sum of the time it takes to perform all these steps. While simple and reliable, this method is only suitable for applications that can tolerate extended periods of unavailability, as the downtime can be hours or even days for very large databases.
Migration Method 2: The Replication and Cutover
This is a modern, low-downtime approach. It involves setting up the target database as a "replica" of the source. The replica continuously receives changes from the source and stays in sync. The migration process is: 1. Set up replication (can be done online with no downtime). 2. Wait for the replica to be fully caught up. 3. (Begin Downtime) Briefly stop writes to the source database. 4. Wait for the final few changes to replicate to the target. 5. Point your application to the new target database. 6. (End Downtime). As the calculator shows, this reduces downtime from hours to just the few minutes or seconds required for the final cutover.
Key Factors Influencing Downtime
Several factors determine the length of your downtime. **Data Volume:** Larger databases naturally take longer to copy. **Network Throughput:** The speed of the connection between your source and target is a major bottleneck, especially for cloud migrations. **Migration Method:** As discussed, this is the most critical choice. **Replication Lag:** In a replication setup, this is the delay between a write occurring on the source and it being applied on the replica. Minimizing lag is key to a fast cutover. **Testing and Automation:** A well-rehearsed, automated migration script will always be faster and less error-prone than a manual process.
Towards Zero-Downtime: Advanced Techniques
For the most critical systems, even a few minutes of downtime is unacceptable. Advanced techniques can achieve near-zero downtime. This often involves using a proxy layer (like ProxySQL) to manage connections, allowing for a rolling cutover where traffic is gradually shifted from the old database to the new one. Another method is using a dual-write system, where the application writes to both the old and new databases simultaneously for a period, ensuring they stay in sync before the final switch. These methods are highly complex and require significant engineering investment but are the gold standard for mission-critical services.