> For the complete documentation index, see [llms.txt](https://docs.vergeos-demo.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.vergeos-demo.com/learn-the-platform/module-10-scenario-labs/lab-hci-compute.md).
# Lab: HCI + Compute Deployment
## Objective
Deploy VergeOS in an HCI + Dedicated Compute configuration using the Terraform playground. You will provision a two-cluster topology — an HCI foundation cluster (controller + storage) and a dedicated compute-only cluster — then configure workload placement across clusters, validate independent compute scaling, and compare the operational model to pure HCI deployments.
## Prerequisites
* Completed all prior modules (1–9)
* Completed the HCI Deployment Lab and UCI Deployment Lab
* Access to the vergeos-terraform-playground repository (cloned locally)
* Terraform CLI installed and configured
* A VergeOS environment or lab that supports nested deployments
* Familiarity with Terraform basics (init, plan, apply)
## Difficulty
**Intermediate** — Requires understanding of VergeOS cluster architecture, multi-cluster networking, and basic Terraform usage
## Estimated Time
**1.5 hours**
***
## Background: HCI + Dedicated Compute Architecture
Before starting the lab, review the two-cluster model that defines HCI + Dedicated Compute:
```mermaid
graph TB
subgraph "Cluster 1: HCI (Controller + Storage ± Compute)"
N1["Node 1
Controller + Storage
Tier 0 + Tier 1"]
N2["Node 2
Controller + Storage
Tier 0 + Tier 1"]
N3["Node 3 (optional)
HCI Node
Storage + Compute*"]
N4["Node 4 (optional)
HCI Node
Storage + Compute*"]
end
subgraph "Cluster 2: Compute Only"
N5["Node 5
Compute Only"]
N6["Node 6
Compute Only"]
N7["Node 7
Compute Only"]
N8["Node 8+
Compute Only (scale)"]
end
CoreNet["Core Network
25–100 GbE"]
N1 --- CoreNet
N2 --- CoreNet
N3 --- CoreNet
N4 --- CoreNet
N5 --- CoreNet
N6 --- CoreNet
N7 --- CoreNet
N8 --- CoreNet
```
**Key principles:**
* **Cluster 1 (HCI)** always includes Nodes 1 & 2 with controllers and Tier 0 storage. Optional Nodes 3–4 add storage and (optionally) compute capacity.
* **Cluster 2 (Compute Only)** contains nodes dedicated entirely to running workloads — no storage overhead, maximum resources for VMs.
* The **Compute toggle** on the HCI cluster controls whether HCI nodes can also run workloads alongside storage/control functions.
* All compute-node storage I/O traverses the core network to the HCI cluster, making inter-cluster bandwidth critical.
***
## Steps
### Part 1: Review the HCI + Compute Topology
Understand the configuration before deploying.
1. In the terraform playground repository, navigate to the `examples/` directory and identify the HCI + Compute `.tfvars` file (look for files referencing "hci-compute" or "hybrid" topologies)
2. Examine the variables and identify:
* How many clusters are defined and their roles (HCI vs compute-only)
* Node count and assignments per cluster
* The **Compute toggle** setting on the HCI cluster — is it enabled or disabled?
* Storage tier configuration (Tier 0 for metadata on controller nodes, Tier 1 for workload data)
* Network configuration for inter-cluster communication
3. Compare this `.tfvars` file with the pure HCI configurations from the previous lab. Note the structural differences:
* Additional cluster definition for compute-only nodes
* Storage tier assignment — compute-only nodes have no storage tiers
* Network bandwidth requirements between clusters
4. Review the deployment scenario documentation (`docs/deployment-scenarios.md`) for the HCI + Compute section
### Part 2: Deploy the HCI + Compute Topology
Provision the two-cluster environment.
1. Run `terraform init` to initialize the provider (if not already done)
2. Run `terraform plan -var-file=.tfvars` and carefully review the planned resources:
* Verify two separate clusters will be created
* Confirm node assignments match the expected topology
* Check that storage tiers are only assigned to HCI cluster nodes
* Validate network interfaces are configured for inter-cluster communication
3. Run `terraform apply -var-file=.tfvars` to deploy
4. Log into the VergeOS UI and verify the deployment:
* **Clusters:** Both clusters appear — one labeled HCI, one labeled Compute
* **Nodes:** Each node is assigned to its correct cluster
* **Storage:** vSAN storage pools exist only on the HCI cluster; compute-only nodes show no storage
* **Networking:** Core fabric network connects both clusters; inter-cluster connectivity is established
* **Controllers:** Controller VMs are running on Nodes 1 and 2 in the HCI cluster
### Part 3: Configure Workload Placement
Practice placing workloads across the two-cluster topology.
1. **Create a VM on the compute-only cluster:**
* In the VergeOS UI, create a new VM and select the compute-only cluster for placement
* Assign CPU and memory resources
* Attach a virtual disk — note that the storage is provisioned from the HCI cluster's vSAN even though the VM runs on a compute-only node
* Start the VM and verify it boots successfully
2. **Create a VM on the HCI cluster** (if Compute is enabled):
* Create a second VM, this time placing it on the HCI cluster
* Compare the resource availability between the two clusters
* Note the difference: HCI nodes share resources between storage/control and compute, while compute-only nodes dedicate all resources to workloads
3. **Relocate a VM to a different cluster:**
* Pick a VM running on the compute-only cluster and shut it down (cluster assignment cannot be changed while the VM is running)
* Edit the VM and change the **Cluster** field to the HCI cluster, then power the VM back on
* Repeat in the opposite direction (HCI → compute-only) if desired
* Document the constraints: cross-cluster relocation requires the VM to be stopped and is **not** state-preserving — the VM is shut down and restarted on the target cluster
* Contrast this with the in-UI **Migrate** action, which is intra-cluster only (it selects a target **node** within the VM's current cluster) and can be performed live without stopping the VM
4. **Monitor inter-cluster I/O:**
* Open the VergeOS dashboard and navigate to network monitoring
* Observe the storage I/O traffic flowing from compute-only nodes to the HCI cluster
* Note the bandwidth utilization on the core network — this is why inter-cluster bandwidth planning is critical
### Part 4: Validate Independent Compute Scaling
Demonstrate the scaling advantage of the HCI + Compute model.
1. **Review compute-only cluster capacity:**
* In the VergeOS UI, check the total CPU and memory available on the compute-only cluster
* Compare this to the HCI cluster's available compute resources (after storage/control overhead)
* Document the effective compute capacity difference
2. **Simulate a scale-out scenario:**
* Review the `.tfvars` file and identify how to add additional compute-only nodes
* Modify the node count for the compute-only cluster (e.g., add 1–2 more nodes)
* Run `terraform plan` to preview the change — note that only compute nodes are added; storage is unaffected
* Apply the change and verify the new nodes join the compute-only cluster
* Confirm that the HCI cluster is completely unchanged — no rebalancing, no storage disruption
3. **Compare scaling models:**
| Scaling Action | Pure HCI | HCI + Compute |
| ---------------------- | ------------------------------------- | ------------------------------------------------- |
| Add compute capacity | Must add full HCI node (with storage) | Add lightweight compute-only node |
| Add storage capacity | Add HCI node or expand existing disks | Add node to HCI cluster only |
| Scale independently | ❌ Compute and storage coupled | ✅ Compute scales independently |
| Hardware flexibility | All nodes need storage-class hardware | Compute nodes optimized for workloads |
| Operational complexity | Simple — single cluster | Moderate — two clusters, inter-cluster networking |
### Part 5: Explore the Compute Toggle
Understand the impact of the HCI cluster's Compute setting.
1. **Check the current Compute toggle state:**
* In the VergeOS UI, navigate to the HCI cluster settings
* Identify whether the Compute toggle is currently enabled or disabled
* If enabled, note which workloads (if any) are running on HCI nodes
2. **Understand the two modes:**
| Setting | Behavior | Best For |
| -------------------- | ------------------------------------------------- | ------------------------------------------------------------------------------- |
| **Compute Enabled** | HCI nodes run workloads alongside storage/control | Smaller deployments where maximizing utilization is preferred |
| **Compute Disabled** | HCI cluster dedicated to storage and control only | Performance-sensitive environments where storage/compute isolation is preferred |
3. **Document your recommendation:**
* Based on the current deployment size, which Compute toggle setting would you recommend?
* What factors would cause you to change the setting?
* Note: Changing the Compute toggle may require a rolling restart of nodes in the HCI cluster — review the impact with VergeOS support before making this change in production
### Part 6: Design Decision Exercise
Apply what you've learned to a real-world scenario.
1. **Scenario:** A customer currently runs a 4-node VergeOS HCI cluster. They need to add 50 new VMs for a development environment but don't need additional storage. Their current storage utilization is only 40%, but CPU is at 75%.
2. **Evaluate the options:**
* **Option A:** Add 2 more HCI nodes (6-node HCI cluster)
* **Option B:** Add a 2-node compute-only cluster (4-node HCI + 2-node compute)
* **Option C:** Migrate to full UCI architecture
3. **For each option, document:**
* Hardware cost implications
* Operational complexity change
* Network requirements
* Future scalability path
* Your recommendation with justification
4. **Bonus:** Identify which terraform playground example most closely matches Option B, and list the `.tfvars` modifications needed to match the customer's requirements
***
## Cleanup
When finished with the lab:
1. Remove all test VMs created during the lab
2. Run `terraform destroy` to tear down the entire HCI + Compute deployment
3. Verify all resources have been cleaned up in the VergeOS UI
***
## Verification
Your HCI + Compute deployment lab is complete when you can answer **yes** to all of the following:
* [ ] Successfully deployed a two-cluster HCI + Compute topology via Terraform
* [ ] Verified cluster roles (HCI vs compute-only), storage allocation, and networking in the VergeOS UI
* [ ] Created VMs on the compute-only cluster and confirmed storage was served from the HCI cluster
* [ ] Monitored inter-cluster storage I/O traffic on the core network
* [ ] Successfully scaled the compute-only cluster independently (added nodes without affecting storage)
* [ ] Documented the Compute toggle behavior and your recommendation for the deployment
* [ ] Completed the design decision exercise comparing HCI, HCI+Compute, and UCI options
* [ ] Cleaned up all lab resources with `terraform destroy`
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.vergeos-demo.com/learn-the-platform/module-10-scenario-labs/lab-hci-compute.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.