To deliver applications and desktops to 10,000 concurrent users in a Citrix Virtual Apps and Desktops environment, the architecture needs to be highly scalable and fault-tolerant. Here’s a rough guide to the infrastructure components required for such an environment:
1. Delivery Controllers
Citrix Delivery Controllers (DCs) are responsible for brokering user sessions, managing the connections between users and their applications or desktops.
- Recommended: 6–8 Delivery Controllers.
- Rationale: Each Delivery Controller can typically handle around 1,500–2,000 concurrent users, but redundancy is essential for high availability (N+1 configuration). For 10,000 users, having 6–8 controllers ensures load balancing and fault tolerance.
2. StoreFront Servers
Citrix StoreFront Servers deliver the app and desktop catalogs to users and provide the interface for launching resources.
- Recommended: 4–6 StoreFront Servers (in a load-balanced configuration).
- Rationale: Each StoreFront server can typically handle around 2,500 concurrent users. To ensure high availability and fault tolerance, at least 4-6 servers in a load-balanced setup are recommended.
3. Active Directory (AD) Domain Controllers
Active Directory is critical for user authentication and resource access. It’s also important for Group Policy management, user accounts, and security.
- Recommended: 2–4 AD Domain Controllers.
- Rationale: You’ll need multiple (typically 2–4) domain controllers spread across availability zones or datacenters to ensure redundancy and fault tolerance. Citrix environments are highly dependent on AD for authentication, so redundancy is key.
4. SQL Database
The Citrix SQL Database (usually Microsoft SQL Server) is the heart of the infrastructure, storing site configuration and data on sessions, connections, etc.
- Recommended: SQL Server in a high-availability configuration (e.g., Always On availability groups or SQL clustering).
- Rationale: The size and complexity of the environment warrant using SQL Server with at least 2–3 database servers in a highly available cluster or SQL Always On. SQL should also be scaled vertically to handle the load (multiple CPUs, large memory).
5. Hypervisors (XenServer/Hyper-V/VMware)
Hypervisors host the Virtual Delivery Agents (VDAs) that provide the applications and desktops.
- Recommended: 50–75 Hypervisor Hosts.
- Rationale: Each hypervisor host can typically host around 150–200 virtual machines, depending on hardware specs (e.g., dual-CPU, high-memory servers with fast SSD storage). For 10,000 concurrent users, if each user session requires 1-2 vCPUs and 4–8 GB of RAM, you would need around 50–75 hosts depending on the load.
6. License Server
The Citrix License Server manages and distributes Citrix licenses to users.
- Recommended: 1 License Server (with a backup/failover).
- Rationale: One primary License Server with a failover (secondary) server should be sufficient for 10,000 users. It should be properly sized, but the License Server does not typically consume many resources.
7. Virtual Delivery Agents (VDAs)
VDAs are installed on the machines that will host the virtual desktops or applications.
- Recommended: Based on machine catalogs and workload, likely spread across multiple machine catalogs based on user groups and types of applications/desktops being delivered.
- Rationale: 10,000 concurrent users will require machine catalogs that are adequately provisioned and load-balanced, with application and desktop pools appropriately sized and distributed.
8. Citrix ADC (NetScaler)
To handle traffic from remote and external users, Citrix ADC (NetScaler) is required to provide secure access, SSL offloading, and load balancing.
- Recommended: 2–4 Citrix ADC appliances (in HA mode).
- Rationale: Citrix ADC should be deployed in pairs (for high availability) and scaled to handle up to 10,000 concurrent connections. High-throughput models should be chosen to handle peak traffic loads.
9. File Servers
File servers for user profile data, home drives, and shared data are essential for storing user data.
- Recommended: 2–4 File Servers with DFS for high availability.
- Rationale: File servers or network-attached storage (NAS) should be used for user profile data (e.g., FSLogix or Citrix Profile Management), document storage, and shared files. Distributed File System (DFS) for high availability is also recommended.
10. Profile Management
Citrix User Profile Management or FSLogix is critical for handling user profiles and providing fast login times.
- Recommendation: Ensure high availability for profile management solutions with sufficient storage and performance to handle 10,000 profiles.
11. Monitoring and Management
Tools like Citrix Director and Citrix ADM (Application Delivery Management) are required to monitor performance, diagnose issues, and scale the environment.
- Recommendation: Deploy monitoring tools across your environment for real-time insights and proactive management of resources and performance.
Summary of Components for 10,000 Concurrent Users:
Component | Quantity (Approx) |
Delivery Controllers | 6–8 Controllers |
StoreFront Servers | 4–6 Servers (load-balanced) |
AD Domain Controllers | 2–4 Domain Controllers |
SQL Database Servers | 2–3 Servers (in HA configuration) |
Hypervisors | 50–75 Hypervisors |
License Server | 1 Primary, 1 Backup |
Citrix ADC (NetScaler) | 2–4 Appliances (in HA mode) |
File Servers | 2–4 Servers (DFS for high availability) |
Profile Management | FSLogix or Citrix UPM with HA Storage |
Monitoring Tools | Citrix Director and Citrix ADM |
Key Considerations:
- Load Balancing: Ensure all key components like Delivery Controllers, StoreFront servers, and Citrix ADC are load-balanced for redundancy.
- High Availability (HA): Use N+1 or N+2 configurations where possible, especially for critical components like Delivery Controllers, SQL Servers, and StoreFront servers.
- Performance Tuning: Each component needs to be properly sized for performance, including CPU, memory, network bandwidth, and storage.
This setup can provide a robust, scalable environment for delivering apps and desktops to 10,000 concurrent users while ensuring high performance, security, and reliability.