BCDR for Azure Virtual Desktop – Cloud Adoption Framework

Table of Contents0.1 In this article1 Design considerations1.1 Host pool active-active vs. active-passive1.2 Host pool resiliency1.3 Optimal storage for profile and office containers1.3.1 User data storage replication and resiliency1.4 Golden image availability1.5 Backup protection1.6 Infrastructure and application dependencies2 Design recommendations Article 08/09/2021 9 minutes to […]

Azure Virtual Desktop is a Microsoft-managed service that provides a control plane for your desktop virtualization environment. The service is free of charge and Microsoft doesn’t offer a financially backed service-level agreement (SLA). Despite having no SLA, we try to achieve at least 99.9% availability for the Azure Virtual Desktop service URLs.

A good BCDR strategy keeps your critical applications and workload up and running during planned and unplanned service or Azure outages. Your strategy should consider resources that are deployed in your subscription as part of the Azure Virtual Desktop data plane, like host pools and storage.

To ensure business continuity, Azure Virtual Desktop also preserves customer metadata during region outages. If there is an outage, the service infrastructure components fail over to the secondary location and continue functioning as normal.

For more information on BCDR considerations for your Azure resources, see Set up a business continuity and disaster recovery plan.

Design considerations

Host pool active-active vs. active-passive

For an Azure Virtual Desktop host pool, you can adopt either an active-active or active-passive BCDR approach.

An active-active approach:

  • Storage outages are mitigated without requiring the user to reauthenticate.
  • Continuous testing of the disaster recovery location is enabled.
  • A single host pool can contain VMs from multiple regions. In this scenario, usage of cloud cache is required to actively replicate the user’s FSLogix profile and office containers between the regions.
  • For virtual machines (VMs) in each region, the cloud cache registry entry specifying locations needs to be inverted to give precedence to the local one.
  • Load balancing of incoming user connection can’t take proximity into account; all hosts will be equal and users may be directed to a remote (not optimal) Azure Virtual Desktop host pool VM.
  • This configuration is limited to a pooled (shared) host pool type. For a personal (dedicated) type, once a desktop is assigned to a user on a certain session host VM, it sticks and doesn’t change, even if not available.
  • This configuration can be complex and isn’t considered to be either a performance or cost optimization.

With active-passive:

  • Azure Site Recovery or a secondary host pool (hot stand-by) can be used to maintain a backup environment.
  • Azure Site Recovery is supported for both personal (dedicated) and pooled (shared) host pool types, and lets you maintain a single host pool entity.
  • You can create a new host pool in the failover region while keeping all of the resources turned off. For this method, set up new application groups in the failover region and assign users to them. You can then use a recovery plan in Azure Site Recovery to turn on host pools and create an orchestrated process.

Host pool resiliency

For host pool VM resiliency:

  • Different options are available when creating a new Azure Virtual Desktop host pool.

  • It’s important to select the right option based on your requirements during creation. These options can’t be changed later.

  • The default resiliency option for Azure Virtual Desktop host pool deployment is Availability Set. This option only ensures host pool resiliency at the single Azure datacenter level, with formal 99.95 percent high-availability SLA.

  • Using Availability Zones, VMs in the host pool are distributed across different datacenters. VMs are still inside the same region, and have higher resiliency and higher formal 99.99 percent high-availability SLA. Your capacity planning should take into account enough extra compute capacity to ensure Azure Virtual Desktop continues to operate even if a single zone is lost.

    Note

    An Azure Resource Manager (ARM) template must be used to specify zones. This option isn’t available yet in the Azure portal.

Before approaching BCDR planning and design for Azure Virtual Desktop, consider which applications accessed via Azure Virtual Desktop are critical. You might want to separate them from non-critical applications so you can provision multiple host pools with a different disaster recovery approaches and capabilities.

Optimal storage for profile and office containers

The location of storage used for FSLogix containers is critical to ensure the lowest latency from the host pool VM. The FSLogix agent can support multiple profile locations for higher resiliency if you configure the VHDLocations registry entry. You can use cloud cache or ensure that a proper replication mechanism is in place based on the storage type used.

Azure offers multiple storage solutions that you can use to store your FSLogix profile and office container:

  • Storage options for FSLogix profile containers in Azure Virtual Desktop compares the different managed storage solutions available.
  • Azure Files or Azure NetApp Files offers the most value to customers, simplifying management of Azure Virtual Desktop. This is the preferred storage solution for this workload.
  • Storage Spaces Direct is also supported with FSLogix and Azure Virtual Desktop. It’s a self-managed storage solution that’s out of scope for this article.

User data storage replication and resiliency

In case of an outage, you can reduce the time required to back up, restore, and replicate data by:

  • Separating the user profile and office container disks. FSLogix offers the option to place disks in separate storage locations.

  • In normal usage, the office disk can consume many more gigabytes than the profile disk and the office disk isn’t required to be resilient. It’s a cache of data and can be downloaded again from Microsoft 365 online services.

  • OneDrive can be used to redirect well-known folders (Desktop, Documents, Pictures, Screenshots, and Camera Roll) if present. This redirection enables the resilience of this data without needing special consideration in a BCDR scenario.

  • Backup, replication, and restore of the profile disk is quicker without the inclusion of the cache data.

    Note

    The FSLogix cloud cache feature is write back by design. This design uses asynchronous replication, which increases performance characteristics to high latency targets.

Multiple replication mechanisms and strategies can be used for user data in FSLogix containers.

  • Profile pattern #1: Native Azure Storage replication mechanisms. For example geo-redundant storage (GRS) for standard file shares, cross-region replication of Azure NetApp Files, or Azure File Sync for VM-based file servers.

  • Profile pattern #2: FSLogix cloud cache has a built-in automatic mechanism to replicate containers between up to four different storage accounts.

  • Profile pattern #3: Only set up geo-disaster recovery for application data and not for user data or profile containers. Store important application data in separate storages, like OneDrive or other external storage with its own built-in disaster recovery mechanism.

Golden image availability

If you use custom images to deploy Azure Virtual Desktop host pool VMs, it’s important to ensure those artifacts are available in all regions if there’s a major disaster. Use the Azure Shared Image Gallery service to replicate images across all regions where a host pool is deployed with redundant storage and multiple copies.

Backup protection

Preventing data loss for critical user data is important.

  • Assess which data needs to be saved and protected. If you’re using OneDrive or some other external storage, saving the user profile or office container data might not be necessary.
  • Consider the appropriate mechanism to provide protection for critical user data.
  • You can use the Azure Backup service to protect profile and office container data when stored in either Azure Files Standard tier or Premium tier.
  • You can use Azure NetApp Files snapshots and policies for Azure NetApp Files on all tiers.
  • You can use Azure Backup to protect host pool VMs. This practice is supported even if host pool VMs are stateless.

Infrastructure and application dependencies

If users of the Azure Virtual Desktop infrastructure need on-premises resource access, it’s critical that you consider the high availability of network infrastructure required to connect. Assess and evaluate the resiliency of authentication infrastructure and consider BCDR aspects for dependent applications and other resources. These considerations will help to ensure availability in the secondary disaster recovery location.

Design recommendations

The following are best practices for your design:

  • For the Azure Virtual Desktop host pool compute deployment model BCDR, use the active-passive option if it satisfies your requirements for recovery point objective (RPO) and recovery time objective (RTO).
  • Azure Site Recovery is recommended for personal (dedicated) host pools. The target region should be aligned with the disaster recovery of the storage backend used by FSLogix.
  • Azure Site Recovery is also supported for pooled (shared) host pools. This option can be evaluated and compared to the deployment of another host pool in the secondary disaster recovery region.
  • When maximum resiliency of the host pool is required in a single region, use Availability Zones. Verify the Availability Zones feature availability in the specific region, and availability of the specific VM SKU inside all the zones.

We recommend storing FSLogix user profile and office containers on Azure Files or Azure NetApp Files for most scenarios.

  • Split user profile and office containers.

  • The recommended options for container storage types are (in order): Azure Files Premium tier, Azure NetApp Files Standard tier, and Azure NetApp Files Premium tier.

  • The recommended storage type depends on the resources and latency required by the specific workload.

  • For optimal performance, place FSLogix containers on storage close to the VM the user is logged on to. Keeping the containers in the same datacenter is best.

  • Use Azure Storage built-in replication mechanisms for BCDR when possible for less critical environments.

    • Use zone-redundant storage (ZRS) or GRS for Azure Files.
    • Use LRS with local only resiliency if no zone/region protection is required.

Note

GRS isn’t available with Azure Files Premium tier or Standard tier with large file support enabled.

  • Only use cloud cache when:

    • The user profile or office container data availability requires high-availability, or an SLA is critical and must be resilient to region failure.
    • The selected storage option can’t satisfy BCDR requirements. For example, GRS isn’t available with Azure Files Premium tier or Standard tier with large file support enabled.
    • Replication between disparate storage is required.
  • We recommend the following guidelines when using cloud cache:

    • Use a solid-state drive (SSD) for the managed disk of the Azure Virtual Desktop host pool VMs.
    • Have a backup solution in place to protect user profile and office containers.
    • Make sure that the managed disk for the local VM is large enough to accommodate the local cache of all user’s FSLogix profile and office containers.
  • Use an Azure Shared Image Gallery to replicate golden images to different regions.

    • The storage used for image creation should be zone-redundant storage (ZRS). At least two copies per region should be maintained.
  • Use Azure Backup to protect critical user data from data loss or logical corruption when using either Azure Files Standard tier or Premium tier.

    • Use snapshots and policies when using the Azure NetApp Files service.
    • Even if supported, using Azure Backup to save your VM state in the host pool isn’t recommended since it should be stateless.
  • Carefully review your resiliency and BCDR plans for dependent resources. These resources include networking, authentication, applications, and other internal services in Azure or on-premises.

    • Network infrastructure, as part of hub and spoke or virtual wide area network (WAN) architecture, must be available in the secondary region.
    • Hybrid connectivity must be highly available in both the primary and secondary regions.
    • Active Directory authentication must be available in the disaster recovery region, or connectivity to the on-premises domain must be guaranteed.

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