In this episode, the hardest part of your cloud migration is moving your data to the cloud. Moving your data to the cloud, without suffering planned or unplanned downtime, can be a challenge. I’m going to give you three strategies that will help you avoid downtime during the migration of your critical application data to the cloud. And in Tech Tapas, we are going to take a look at what it means to fly two mistakes high, and how that relates to application availability. Links and More Information The following are links mentioned in this episode, and links to related information: 3 Strategies to Avoid Downtime When Migrating Data to the Cloud (https://blog.newrelic.com/engineering/migrating-data-to-cloud-avoid-downtime-strategies/ (https://blog.newrelic.com/engineering/migrating-data-to-cloud-avoid-downtime-strategies/)) Modern Digital Applications Website (https://mdacast.com (https://mdacast.com)) Lee Atchison Articles and Presentations (https://leeatchison.com (https://leeatchison.com)) Architecting for Scale, published by O’Reilly Media (https://architectingforscale.com (https://architectingforscale.com)) Main Story - 3 Strategies to Avoid Downtime when Migrating Data to the Cloud Moving your data is one of the trickiest parts of a cloud migration. During the migration, the location of your data can have a significant impact on the performance of your application. During the data transfer, keeping the data intact, in sync, and self-consistent requires either tight correlation or—worse—application downtime. Moving your data and the applications that utilize the data at the same time is necessary to keep your application performance acceptable. Deciding how and when to migrate your data relative to your services, though, is a complex question. Often companies will rely on the expertise of a migration architect, which is a role that can greatly contribute to the success of any cloud migration. Whether you have an on-staff cloud architect or not, there are three primary strategies for migrating application data to the cloud: Offline copy migration Master/read replica switch migration Master/master migration It doesn’t matter if you’re migrating an SQL database, a noSQL database, or simply raw data files—each migration method requires a different amount of effort, has a different impact on your application’s availability, and presents a different risk profile for your business. Strategy 1: Copy Data While Application is Offline An offline copy migration is the most straightforward method. Bring down your on-premise application, copy the data from your on-premise database to the new cloud database, then bring your application back online in the cloud. An offline copy migration is simple, easy, and safe, but you’ll have to take your application offline to execute it. If your dataset is extremely large, your application may be offline for a significant period of time, which will undoubtedly impact your customers and business. For most applications, the amount of downtime required for an offline copy migration is generally unacceptable. But if your business can tolerate some downtime, and your dataset is small enough, you should consider this method. It’s the easiest, least expensive, and least risky method of migrating your data to the cloud. Strategy 2: Read Replica Switch The goal of a read replica switch migration is to reduce application downtime without significantly complicating the data migration itself. For this type of migration, you start with your master version of your database running in your on-premise data center. You then set up a read replica copy of your database in the cloud with one way synchronization of data from your on-premise master to your read replica. At this point, you still make all data updates and changes to the on-premise master, and the master synchronizes those changes with the cloud-based read replica. The master-replica model is common in most database systems. You’ll...