Update disaster recovery guidance #198
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| @@ -7,7 +7,7 @@ weight: 40 | |||
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| This document is intended to list technical risks to our digital services and the mitigations we have in place. | |||
| This document is intended to list technical risks to our digital services and the mitigations we have in place.<br/><br/>For any issue affecting a service (or services) always [check if there are any dependant services](https://educationgovuk.sharepoint.com/sites/teacher-services-infrastructure/SitePages/Teacher-services-dependencies.aspx) that may also be affected. | |||
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| This document is intended to list technical risks to our digital services and the mitigations we have in place.<br/><br/>For any issue affecting a service (or services) always [check if there are any dependant services](https://educationgovuk.sharepoint.com/sites/teacher-services-infrastructure/SitePages/Teacher-services-dependencies.aspx) that may also be affected. | |
| This document is intended to list technical risks to our digital services and the mitigations we have in place.<br/><br/>For any issue affecting a service (or services) always [check if there are any dependent services](https://educationgovuk.sharepoint.com/sites/teacher-services-infrastructure/SitePages/Teacher-services-dependencies.aspx) that may also be affected. |
| |Impact|Applications may be unavailable. Data may be lost.| | ||
| |Prevention|Approved PIM request required for production Azure access.<br/>Pull Requests require at least 1 approval.<br/>Soft delete and versioning enabled for key vaults and storage accounts.<br/>Azure resource locks placed on important resources [Azure locks](https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/lock-resources?tabs=json). | | ||
| |Detection|Endpoint monitoring may point to a healthcheck page that is now failing. Or smoke tests running in production may detect it.| | ||
| |Remediation|Recovery dependant on the resource deleted, either restore correct version or redeploy and restore data from backup| |
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| |Remediation|Recovery dependant on the resource deleted, either restore correct version or redeploy and restore data from backup| | |
| |Remediation|Recovery dependent on the resource deleted, either restore correct version or redeploy and restore data from backup| |
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sorry! a dependant is a person who is dependent on someone
| ## Loss of Azure/AWS availability zone | ||
| We deploy to the UK South or West Europe regions which have 3 separate availability zones (AZ). It may happen that one of them is unavailable: either network, compute or storage services are affected. | ||
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| |Impact|Applications may be slow or unavailable| | ||
| |Prevention|Applications should be built with failure in mind: deploy multiple application instances and deploy databases in cluster mode. Spread them across multiple AZs for high availability.<br/>Our AKS clusters are spread across 3 AZs. Scale applications to more than 1 replicas and enable zone redundancy.| | ||
| |Prevention|Applications should be built with failure in mind: AKS clusters should be configured with nodes spread across multiple AZS. AKS Deployments should use a zone topology spread constraint. Scale applications to more than 1 replica to enable zone redundancy.<br/>Azure storage accounts should be ZRS or GZRS if zone redundancy is required (automatic and manual failover).<br/>Azure key vault uses replication within region and to a paired region (automatic failover).<br/>Azure Postgres can be configured zone redundant, with the active/standby instances in different zones.<br/>Azure Redis can be zone redundant only if using the Premium SKU.<br/>Postgres and Redis utilise automatic failover. Postgres can also be failed over manually.<br/>Cluster Public IP addresses should be configured with zone redundancy [Azure PIP redundancy](https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/public-ip-addresses#availability-zone)| |
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| |Prevention|Applications should be built with failure in mind: AKS clusters should be configured with nodes spread across multiple AZS. AKS Deployments should use a zone topology spread constraint. Scale applications to more than 1 replica to enable zone redundancy.<br/>Azure storage accounts should be ZRS or GZRS if zone redundancy is required (automatic and manual failover).<br/>Azure key vault uses replication within region and to a paired region (automatic failover).<br/>Azure Postgres can be configured zone redundant, with the active/standby instances in different zones.<br/>Azure Redis can be zone redundant only if using the Premium SKU.<br/>Postgres and Redis utilise automatic failover. Postgres can also be failed over manually.<br/>Cluster Public IP addresses should be configured with zone redundancy [Azure PIP redundancy](https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/public-ip-addresses#availability-zone)| | |
| |Prevention|Applications should be built with failure in mind: AKS clusters should be configured with nodes spread across multiple AZs. AKS Deployments should use a zone topology spread constraint. Scale applications to more than 1 replica to enable zone redundancy.<br/>Azure storage accounts should be ZRS or GZRS if zone redundancy is required (automatic and manual failover).<br/>Azure key vault uses replication within region and to a paired region (automatic failover).<br/>Azure Postgres can be configured zone redundant, with the active/standby instances in different zones.<br/>Azure Redis can be zone redundant only if using the Premium SKU.<br/>Postgres and Redis utilise automatic failover. Postgres can also be failed over manually.<br/>Cluster Public IP addresses should be configured with zone redundancy [Azure PIP redundancy](https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/public-ip-addresses#availability-zone)| |
| @@ -65,7 +75,7 @@ In some rare cases, an entire region might become unavailable. | |||
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| |Impact|Applications may be unavailable| | |||
| |Prevention|For critical applications, it is possible to deploy to 2 different regions, synchronise the data, configure a DNS based failover or GSLB. We don’t usually protect against this risk as it is not worth the complexity of the required set-up.| | |||
| |Prevention|For critical applications, it is possible to deploy to 2 different regions, synchronise the data, configure a DNS based failover or GSLB. We don’t usually protect against this risk as it is not worth the complexity of the required set-up.<br/>Production Postgres backups are kept in a GRS Azure storage account, which maintains copies of data in a separate reqion. Any critcal application data kept in a storage account should be GRS/GZRS.<br/>Azure Key Vault maintains a copy of the contents in another region.<br/>For storage accounts and key vaults, failover is automatic and transparent. Storage accounts also support manual failover. | | |||
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| |Prevention|For critical applications, it is possible to deploy to 2 different regions, synchronise the data, configure a DNS based failover or GSLB. We don’t usually protect against this risk as it is not worth the complexity of the required set-up.<br/>Production Postgres backups are kept in a GRS Azure storage account, which maintains copies of data in a separate reqion. Any critcal application data kept in a storage account should be GRS/GZRS.<br/>Azure Key Vault maintains a copy of the contents in another region.<br/>For storage accounts and key vaults, failover is automatic and transparent. Storage accounts also support manual failover. | | |
| |Prevention|For critical applications, it is possible to deploy to 2 different regions, synchronise the data, configure a DNS based failover or GSLB. We don’t usually protect against this risk as it is not worth the complexity of the required set-up.<br/>Production Postgres backups are kept in a GRS Azure storage account, which maintains copies of data in a separate region. Any critical application data kept in a storage account should be GRS/GZRS.<br/>Azure Key Vault maintains a copy of the contents in another region.<br/>For storage accounts and key vaults, failover is automatic and transparent. Storage accounts also support manual failover. | |
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Update disaster recovery guidance
https://trello.com/c/g4YUcnbV/1860-dr-update-tech-guidance