Using multiple regions
You can replicate data to multiple regions for high availability scenarios to ensure active-active applications failover models. Multiple regions also ensure application data availability for locality purposes with the added value of cost savings.
Having multiple regions can increase your billed charges. For more information, see Pricing and billing.
Eventual consistency model and multi-region updates
DataStax Astra DB follows the eventual consistency model. Depending on the selected consistency level, data written to one region might not be immediately accessible to other regions in the same database.
If you are using the EACH_QUORUM consistency level for normal updates or SERIAL consistency level for Lightweight Transactions (LWT), then data is immediately accessible on all regions provided the operation successfully completes.
These consistency levels are for only write requests.
For all other consistency levels, data might not be immediately accessible. The time span is normally within a few minutes to fully replicate the data. However, it could take longer, and possibly span one or more days. There are several contributing factors to the latter scenario, such as the workload volume, the number of regions, the data repair operations, and network resources.
Data sovereignty
Astra DB replicates all data in the database to all of a database’s regions. By contrast, multiple keyspaces in Apache Cassandra® and DataStax Enterprise (DSE) allow a database to replicate some tables to a subset of regions. To achieve the same behavior as Cassandra or DSE, create a separate Astra DB instance that adheres to the necessary region restrictions. The database client will need to add a separate connection for the additional database and send queries to the appropriate connection depending on the table being queried.
Add a region to a classic database
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In the Astra Portal navigation menu, go to Databases, and then click your database’s name.
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On the Overview tab, click Add Region.
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Select the region that you want to add.
If you add multiple regions to your database, you can use each region only once.
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Click Add, and then click Confirm.
The database enters Maintenance status while provisioning and replicating data to the new region. Database functionality is limited in Maintenance status. Once provisioning is complete, the database returns to Active status.
Remove a region from a database
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Removing a region deprovisions and deletes all data from that region. Removing a region is irreversable. You can add the region to the database again, but you can’t recover the original region provisioning, configuration, data, or otherwise. |
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In the Astra Portal navigation menu, go to Databases, and click your database’s name.
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On the Overview tab, locate the region you want to remove, click More, and then click Remove Region.
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To verify removal, enter the region’s datacenter ID, as shown in the confirmation dialog.
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Click Remove Region.
The database enters Maintenance status while removing the region. Database functionality is limited in Maintenance status. Once removal is complete, the database returns to Active status.
