Understanding high availability and disaster recovery for IBM Cloudant
IBM® Cloudant® for IBM Cloud® is designed for applications requiring very high availability. Customer data remains readable and writable during zone outages, with no need for customer action, such as failover.
High availabilityThe ability of a service or workload to withstand failures and continue providing processing capability according to some predefined service level. (HA) is the ability for a service to remain operational and accessible in the presence of unexpected failures. Disaster recoveryThe ability of a service or workload to recover from rare, major incidents and wide-scale failures, such as service disruption. This includes a physical disaster that affects an entire region, corruption of a database, or the loss of a service contributing to a workload. The impact exceeds the ability of the high availability design to handle it. is the process of recovering the service instance to a working state.
IBM Cloudant meets the Service Level Objectives (SLO) with the Standard plan.
For more information about the available region and data center locations, see Service and infrastructure availability by location.
High availability architecture
IBM Cloudant provides high-availability by replicating all data across three zones in a region. By doing this, IBM Cloudant keeps your data fully available during infrastructure maintenance, database upgrades, machine failures and zone-level outages.
High availability features
IBM Cloudant supports the following high availability features:
| Feature | Description | Consideration |
|---|---|---|
| Resilient to complete zone outages | Standard on all instances and data remains fully available during a zone or machine failure. | |
| Shard replication | Data is replicated to three zones in a region, ensuring data availability. | |
| Cross-region high availability | IBM Cloudant enables cross-region data redundancy and failover. | Optional. Customers must configure cross-region high availability when needed. |
Disaster recovery architecture
Although data is stored redundantly within an IBM Cloudant cluster, it's important to consider extra backup measures. IBM Cloudant provides a supported tool for snapshot backup and restore. The tool is called CouchBackup, and is open source. For more information, see Introducing CouchBackup.
To implement resilience to full region outages, you can create replication to another IBM Cloudant instance in a different region with bidirectional continuous replication. This supports either active-passive or active-active configuration. For more information, see replication setup for cross-region disaster recovery.
Disaster recovery features
IBM Cloudant supports the following disaster recovery features:
| Feature | Description | Consideration |
|---|---|---|
| Backup and restore | Restore a database from previously created backup; see IBM Cloudant backup and recovery. | Open source tool. Customer configured. |
| Cross-region failover | IBM Cloudant replication helps you build a complete disaster recovery capability. | Customer configured. |
| Live data synchronization | IBM Cloudant bidirectional active-active replication feature helps you build a complete disaster recovery capability. | Customer configured. |
Planning for DR
The DR steps must be practiced regularly. As you build your plan, consider the following failure scenarios and resolutions.
| Failure | Resolution |
|---|---|
| Hardware failure (single point) | IBM Cloudant is resilient to single point of hardware failure; data remains online. No customer configuration required. |
| Zone failure | IBM Cloudant is resilient to zone failures; data remains fully available for read and write during zone failures. |
| Data corruption | IBM Cloudant checks data checksums for when data is read. In the case of corruption, the customer needs to restore from backup. Use the restored database in production. |
| Regional failure | Restore backup to new region. Use the restored database in production. Cross-region replication: failover to replicated instance and continue reads/writes as normal. |
Your responsibilities for HA and DR
It is your responsibility to continuously test your plan for HA and DR.
Interruptions in network connectivity and short periods of unavailability of a service might occur. It is your responsibility to make sure that application source code includes client availability retry logic to maintain high availability of the application.
For more information about responsibility ownership between you and IBM Cloud for IBM Cloudant, see Understanding your responsibilities when you use IBM Cloudant.
Stay informed: IBM notifications
Updates affecting customer workloads are communicated through IBM Cloud notification. Changes that impact customer workloads are detailed in IBM Cloud notifications. For more information about planned maintenance, announcements, and release notes that impact this service, see Monitoring notifications and status.
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Stay updated with Service changes and deprecations and Release notes of IBM Cloudant.