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Resiliency design
High availability design
The web app multi-zone resiliency pattern deploys a 3-tier web architecture in a region following the multi-zone, single-region deployment described in IBM VPC resiliency.
The web tier and application tier are deployed in two availability zones. Each tier is deployed across VPC Virtual Server Instances (VSIs) in a VPC Instance Group for Autoscaling. A public VPC Application Load Balancer (ALB) routes web requests to healthy virtual instances in the app tier. A private VPC ALB routes traffic to healthy virtual servers in the app tier.
The web and app tiers are subject to the 99.9% IBM Cloud infrastructure SLA for a region. For 99.99% infrastructure SLA within the region, deploy the web and app servers across 3 availability zones.
High availability at the database tier is typically achieved with an active-standby architecture that includes:
- A primary database and one or more standby database replicas
- Data replication between the primary and standby replicas
- A mechanism to failover from the primary database to the standby replica and back
In the web app multi-zone resiliency pattern, the database tier is deployed on Virtual Server Instances across two availability zones in the same region, following an active-standby architecture that uses database-specific replication and failover configuration settings.
This database deployment architecture is subject to the 99.9% IBM Cloud infrastructure SLA for a region. For 99.99% infrastructure SLA within the region, the database must be deployed on virtual servers across three availability zones within the region and use clustering and replication configurations that are database-specific and are beyond the scope of this document.
An alternative to deploying the database in VPC Virtual Server Instances is to use IBM Cloud Databases instances in a multi-zone region (MZR). IBM Cloud Databases provides highly available and scalable managed SQL and no-SQL databases with 99.99% SLA and low operational cost.
Backup and restore design
The web app multi-zone resiliency pattern uses backup and restore to protect database contents from accidental deletion or corruption and provide short-term storage for historical data.
Do the following to create transaction-consistent database backups that can be quickly restored in the same region where the Web Application is deployed:
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Use database-aware backup tools, such as IBM Storage Protect, to create and manage database backups.
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Schedule regular automated database backups based on business Recovery Point Objective requirements.
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Schedule regular file-level backups if needed to meet application and business process requirements.
Do the following to enable recovery of the database contents in an alternative site if a regional outage occurs:
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Create backups of the database servers by using IBM Storage Protect to enable recovery of the database application in an alternative site if a regional outage occurs.
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Store database backups in cross-region Cloud Object Storage.