Step 1 of 8 - Virtualization
You're running an estate, not a cluster
Every cluster below was sized for its own peak, so every one of them idles.
Deployment model
4 nodes running 8 vCPU of actual work.
Pooled and sized once for the peak, 7 nodes would average 15.0%. Auto-scaling brings it to 4 nodes at 26.2%, moving between 9.5% and 42.4% across the day against a 38% setpoint.
The arithmetic, in full
| Step | Working | Result |
|---|---|---|
| Provisioned today | 1 cluster of 7 nodes x 8 vCPU | 56 vCPU |
| Mean demand | 56 vCPU x 15.0% estate average utilization | 8 vCPU |
| Aggregate peak | 8.4 vCPU x (1 + (2.23 - 1) / sqrt(1)), a pooled peak-to-mean of 2.228 | 19 vCPU |
| Consolidated, sized once for the peak | max(3, ceil(18.7 vCPU / (8 vCPU x 37.5% target))) = max(3, ceil(6.24)); the mean sits well under that peak | 7 nodes, averaging 15.0% |
| Auto-scaled through the day | the pool follows the pooled curve in whole nodes, 30 minutes behind it, holding its size for 2 hours before shrinking | 4 nodes on average, at 26.2% CPU |
| Utilization across the day | 9.5% to 42.4% against a 37.5% setpoint: the pool runs hot while it's a bucket behind a rise, and cool while the cooldown is still holding capacity after a peak | 9.5%-42.4% |
Assumptions
- 8 vCPU per node. Standalone clusters are drawn around 7 nodes, snapped to an odd number for quorum and held between 3 and 15; this estate is one cluster of 7.
- Each standalone cluster's CPU is a draw from a normal distribution centred on 15.0% and held between 0% and 100%; with one cluster there's nothing to average against, so it sits on 15.0% exactly. The published band is 10-15% today against a 30-45% auto-scaled target, and this Private Host Cluster is set to 37.5%.
- The Private Host Cluster floors at 3 nodes and must reach 7 at peak.
- The auto-scaler sizes for what it saw 30 minutes ago and waits 2 hours before shrinking, so the pool averages 26.2% rather than sitting on its 37.5% setpoint.
- Workloads are independent; consolidation moves where work runs, not how much there is.
What a virtual cluster gives an app team
Its own connection string, databases, schemas, users, roles and backups, and no visibility into the Private Host Cluster or any other virtual cluster.