Capacity planning
Interpret physical resources, reservations, overcommit, and maintenance headroom.
Capacity planning compares configured reservations, observed demand, and the resources needed to survive maintenance or a failure. Infra reports these measurements separately.
Capacity terms
Physical capacity describes installed resources. Host reserve excludes the OS and infrastructure budget. Admission applies pool policy and supported overcommit to derive allocatable capacity, then subtracts existing resource and operation reservations to show headroom.
Observed usage measures what those resources recently consumed. It is useful for sizing and contention diagnosis but does not replace configured reservations. For example, a lightly used guest can still prevent another large guest from fitting on the same node.
Low observed usage does not free a reservation. A 16 GiB droplet still reserves its configured memory when the guest uses only a small portion of it.
Overcommit
A pool's CPU and memory overcommit ratios default to 1.0. Values must be finite
numbers at least 1.0 and within the limits supported by that pool. Unsupported
values are rejected.
Overcommit changes admission calculations. It does not create physical resources. CPU overcommit can increase contention; memory overcommit can cause host pressure or guest termination when the physical system cannot satisfy demand. Use observed pressure and workload requirements when selecting ratios.
Changing a ratio does not resize running guests. Lowering it below current reservations blocks new placements and reports the overallocated state.
Failure-domain headroom
Reserve enough eligible capacity to replace the workloads in the failure domain your service must tolerate. Region-wide free memory is insufficient if required zone spread or CPU compatibility excludes that memory from recovery placement.
Use Fleet → Capacity → Simulate failure to inspect node or zone loss against current placement requirements. The result identifies unschedulable workloads; it does not reserve future hardware or execute recovery.
Migration headroom
Live migration temporarily reserves a destination while the source remains allocated. A fleet at its admission limit can be unable to drain a host. Add capacity or free reservations before scheduling maintenance.
Storage repair similarly requires free eligible space outside the failed replica location. Include snapshot retention, backup staging, and device reserve in storage planning.
Forecasts
Capacity views extrapolate recent reservation or usage changes over a selected period. Forecasts describe that historical trend and should not be treated as a commitment about future demand. Review planned deployments, maintenance, and hardware lead times alongside the chart.
Respond to constraints
Add nodes, expand eligible pools, revise justified placement constraints, or resize workloads through a reviewed procedure. Raising quota removes a project admission limit but does not resolve a physical capacity shortage.
Set alerts on allocatable headroom and storage repair capacity before a maintenance operation needs them.