The booking portal of Nordlicht Reisen GmbH is only as available as the data it runs on. If a data center fails, the booking database is to keep running without losing confirmed bookings, and so are the partners' availability data and the files. This lesson chooses how data is spread across data centers without anyone having to switch over.
Prior knowledge. K4, lesson 4.7.4 shows zone redundancy for the Azure SQL and Blob Storage of the Kladde and calculates the composite availability; the redundancy levels of storage (LRS to GZRS) are set up by AZ-104, lesson 2.1. That is not repeated. The region failure is lesson 3.2 of this course, the backup lesson 3.1. Here it is about the distribution within a region and the decision between the data services.
The requirement
All values are assumptions of the task.
| No. | Requirement | Source | Measure (assumption) |
|---|---|---|---|
| Y1 | Booking database survives a zone failure without losing confirmed bookings | Management | RPO 0, switchover in under a minute |
| Y2 | Partners' availability data (documents, assumption: Azure Cosmos DB) stays readable and writable | Partners | zone failure without intervention, second region for reading |
| Y3 | Files and photos stay reachable during a zone failure | Operations | without intervention, also for the offices' shares |
| Y4 | Everything in the EU, region germanywestcentral |
Data protection | base assumption |