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Installation of Operator Clients
| non-exhaustive list of options | remarks |
|---|---|
| Azure Virtual Desktop | See also: Azure Virtual Desktop for the Operator Client |
| database http proxy using SSL | |
| Citrix | Can be integrated with most cloud providers |
Use of managed services
There is no actual requirement for the Delft-FEWS components to use managed services. Managed services can be used as long performance is not affected. As an example, customers that are using SQLServer database replication between different geographical locations reported database timeouts. In response, we've improved our software, removed database indexes and added reconnection strategy for these problems. Since we expect Delft-FEWS users add many more simultaneous running Forecasting Shell servers in the future, we expect / foresee more challenges in this area. It is much better not to use the automated placement of database indexes.
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On a high level the different scenarios for running Delft-FEWS in a highly available manner when the primary Azure region fails, from most high available to least available
Scenario | Description | Disaster recovery if primary regions fails | Manual interventions | Recover Time/Data Loss for Delft-FEWS components |
Dual MC in 2 Azure regions | 2 different databases in two regions, databases will be synchronized by Delft-FEWS. Use Geo redundant storage for file shares. | Automatically by Delft-FEWS. | Operator clients need to reconnect to secondary MC. This has been pre-configured. | No Recovery Time. (Hot Stand By) Data loss is minimal and can be restored by rerunning workflows. |
Single MC with Database in 2 Azure regions | Azure auto failover group Managed Instance Database with Azure Site Recovery for VMS. Use Geo redundant storage for file shares. | Use Azure Site Recovery to restore VMS in secondary region. Synchronized database will be made primary by Azure.
| Azure Site Recovery has to be enabled. | Recovery Time depends on the time it takes for Microsoft to enable ASR. Data loss is minimal and can be restored by rerunning workflows. |
Single MC with locally redundant Database | Single database with Delft-FEWS components | Database backups have to be restored to a new database in a secondary region. VM backups have to be restored to a secondary region | Database configurations on restored VMs have to be adjusted to new DB. Delft-FEWS configuration has to be adjusted to use new Database. | Recovery time is a few days. Data loss depends on the backup schedules. |
Disaster Recovery
This section will describe possible Disaster Recovery solutions for the different parts of a Virtual Machine based Azure system:
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Workflow Test Runner in Azure Devops
Examples
Deltares has successfully completed Delft-FEWS projects in the cloud with virtual machines using standard installation scripts, using virtual machines with Azure ARM templates and AWS Elastic Beanstalk. For practical reasons, will keep our requirements / installation instructions as cloud neutral as possible.
ARM templates
Example ARM templates have been provided by MDBA and can be found here: MDBA ARM templates download