The Blueprint: Sizing the Perfect Hardware Recommendation for Your 3CX PBX
Choosing the right foundation is key to a stable and high-performing communication system. This guide breaks down the essential hardware requirements for deploying 3CX, ensuring your Private Branch eXchange (PBX) can handle your business’s current and future communication needs.
Understanding Your User Profile
Before diving into specs, let’s define a standard 3CX user (extension):
- They typically use the 3CX Web Client/Windows Softphone App and a 3CX Mobile App.
- They are part of one Department and one Call Queue.
- They may also connect a physical IP phone to their extension.
Crucial Note: These specifications are a baseline. Heavy usage of features like Call Queues and group calls will significantly increase the CPU and RAM demands compared to simple 1-on-1 calling.
General System Requirements
These foundational requirements apply to nearly all 3CX deployments:
🧠 CPU & Memory (RAM)
| Component | Requirement | Key Consideration |
| CPU | Use the suggested Intel CPU families (or equivalent AMD) as a starting point. | Call Queues & Group Calls are CPU-intensive. Size up if you have high call center activity. |
| Memory | Minimum requirements increase with more extensions, groups, and queues. | More Groups & Queues require more RAM. |
🌐 Network
- Connectivity: A minimum of 1Gb LAN is required.
- High-Volume: Deployments with 1000+ extensions need 10Gb network connectivity.
- Voice Quality: It is strongly recommended to implement Quality of Service (QoS) on your network gear to prioritize time-sensitive VoIP traffic, especially in busy, mixed-use environments.
💾 Storage
- Base Install: Allocate at least 40GB for the base 3CX installation.
- Additional Space: Plan for extra storage for:
- Recordings/Voicemail: ~1MB per minute of audio.
- Logging: Verbose logs on a busy system can consume up to ~1GB per day.
- Maintenance:
- Regularly offload (archive) old recordings, voicemails, and backups to cold storage.
- Periodically move old Call History (CDR) data to a remote database to keep the 3CX database fast.
3CX PBX Hardware Sizing Guide
The table below outlines the suggested hardware for x86-based systems, categorized by the number of extensions. x86 includes both “Bare Metal” (physical server) and “Virtual Machine” (VM) deployments.
| PBX Size | Extensions (Up to) | Linux (Debian) | Windows | Storage |
| Small | 10 | 2 vCPUs, 4GB RAM | 2 vCPUs, 4GB RAM | 80 GB SSD |
| Medium | 50 | 4 vCPUs, 4GB RAM | 6 vCPUs, 6GB RAM | 160 GB SSD |
| Large | 250 | 6 vCPUs, 8GB RAM | 8 vCPUs, 10GB RAM | 320 GB SSD |
| Enterprise | 1000 | 8 vCPUs, 16GB RAM | 10 vCPUs, 18GB RAM | 640 GB SSD |
| Enterprise+ | 1000+* | 8+ vCPUs, 32+ GB RAM | 10+ vCPUs, 34+ GB RAM | 640+ GB SSD |
*For deployments exceeding 1000 extensions, please consult with 3CX for specialized planning.
Deployment Type Considerations
🖥️ x86-Based Systems (Bare Metal & VM)
x86 systems require 64-bit architecture compatibility. 3CX supports installation on the following verified HyperVisors:
- VMware vSphere Hypervisor (ESXi) 6.5u1 and above.
- Microsoft Hyper-V Server (6.2) and above.
- Citrix XenServer 7.0 and above.
- KVM 2.8 and up.
☁️ Cloud Provider Instances
If you choose a cloud deployment, select an instance that meets or exceeds the core vCPU and memory requirements above. Here are suggested starting points for the major platforms:
| PBX Size | Google Cloud Platform (GCP) | Microsoft (Azure) | Amazon EC2 | Amazon Lightsail |
| Small (up to 10 ext) | e2-medium | Standard_B2ls_v2 | t3.medium | medium_3_x |
| Medium (up to 50 ext) | e2-medium | Standard_B2ls_v2 | t3.medium | medium_3_x |
| Large (up to 250 ext) | e2-standard-4 | Standard_B4as_v2 | t3.xlarge | xlarge_3_x |
3CX Session Border Controller (SBC) Requirements
If your main 3CX PBX is in the cloud and you need to connect physical IP phones at a remote location, you’ll need a local 3CX SBC.
| Devices Connected (IP Phones) | Platform | CPU Family | vCPUs | Memory (RAM) | Storage |
| Up to 50 | Linux Debian | Intel Core i3+ | 2 | 2GB | 30GB |
| Up to 50 | Windows | Intel Core i3+ | 4 | 4GB | 30GB |
| Up to 100 | Linux Debian | Intel Core i7+ | 4 | 2GB | 30GB |
| Up to 100 | Windows | Intel Core i7+ | 6 | 4GB | 30GB |
SBC Note: This SBC table assumes devices have up to 10 Busy Lamp Fields (BLFs) each.
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