Example of Application Data Migration Scenario

Here's an example of migrating a legacy application that uses Microsoft SQL Server. This instance of SQL Server has AlwaysOn availability groups (AG) feature and is hosted between two hosts, with locally attached disks. Daily backups are stored on a file system and retained for two weeks; weekly backups are stored in the local object store for long-term retention.

To help architect the migration of this application to Oracle Cloud Infrastructure, let's identify application components and answer some of the questions that were discussed earlier. The following diagram describes the application as it resides within the current on-premises environment.

Description of the illustration on_premises_environment.png

A successful move of the application to Oracle Cloud Infrastructure must move both the structured database files and the archive backup data. This is an opportunity to trim the amount of data and purge your archive to meet the data requirements of your business.

Now consider what part of data must be accessed across geographies or availability domains. The current state of the application structure is shown in high availability in a single region. Focusing on the migration of data, availability domains create the redundancy necessary for the application to fail over in a reasonable timeframe.

Description of the illustration data_after_moving_to_oci.png

To reduce latency and ensure performance, keep the block volume within the same fault domain as the SQL Server host.

The data must be highly available, but how much data can actually be lost before the loss starts to significantly impact business operations? SQL Server availability groups manage data loss between the individual databases. This consideration also affects the backup policies for the application. In this example, the backups are occurring on the secondary server, so they don't impact the performance of the primary server.

How many copies of the data is needed to ensure both high availability and business continuance with the application? The organization of the AlwaysOn availability groups within fault domains and availability zones is key when building the new home for the application in Oracle Cloud Infrastructure. Because the object storage is redundant across the region, the decision to replicate the backup data to another region must be part of the business operations model.

Using the Oracle Cloud Infrastructure Object Storage service to replace an offsite tape solution can be accomplished with cross-region replication. Cross-region replication for the backup data and object storage ensures that the data is protected from region-wide outages that might affect the business.