A Quota Error That Is Not a vCPU Quota Error
A private cloud on FusionCloud 8.x with ManageOne serves three departments. Tenant R and D has a project quota of 600 vCPU, 1,200 GB RAM, and 40 TB volume capacity. The AZ1 cluster has eight hosts, each 2 x 24 cores and 768 GB RAM, with a CPU overcommit ratio of 1:3 and memory overcommit of 1:1.5. R and D runs 96 VMs averaging 12 percent CPU and 45 percent memory utilization. Creating the 97th VM fails with quota exceeded, although the project dashboard shows 420 vCPU and 700 GB RAM in use. The tenant administrator asks for the project quota to be raised to 2,000 vCPU. Separately, another project's 20 VMs on two hosts are causing latency spikes for neighbors.
1. Explain the most likely causes of the quota error despite the dashboard showing 420 of 600 vCPU used.
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A quota error is not necessarily a vCPU error. The dashboard usually shows only the headline compute counters, while the create request also consumes other quota objects: number of servers or instances, memory, volume count and capacity, snapshots, floating IPs, security groups, and ports. If any one of these is exhausted, the request fails with a generic quota message. Volume quota is a strong candidate because 40 TB is modest for 96 VMs and snapshots may consume capacity invisibly. A second candidate is project versus tenant quota: the project may be within its own limit while the parent tenant or the AZ capacity is exhausted. A third is that the dashboard is stale or scoped differently from the API call. The correct first step is to read the actual error object and compare every quota dimension for that project, not to raise the vCPU number that is clearly not exhausted.
2. How would you respond to the request to raise the quota to 2,000 vCPU? Show the capacity arithmetic.
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Raising the quota is a policy change, not a capacity change, and 2,000 vCPU is far beyond the physical cluster. The cluster has 8 x 48 = 384 physical cores, and at 1:3 overcommit the schedulable vCPU is about 1,152, before reserving headroom for HA and growth. A 2,000 vCPU project quota would allow the project alone to exceed the cluster, so the quota would stop being a meaningful control and the next failure would be a placement or performance failure. Memory is also relevant: 8 x 768 GB = 6,144 GB, at 1:1.5 overcommit about 9,216 GB, shared across all tenants. I would approve a modest increase only after confirming which quota dimension actually failed, then set it against measured headroom, for example no more than 70 percent of schedulable capacity across all projects, and add alerting at 80 percent consumption.
3. What controls would you add for the noisy-neighbor problem, and how do they interact with quotas?
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Quotas limit how much a tenant can request; they do not limit how much a running VM can disturb others. For the noisy project, use anti-affinity rules to stop its 20 VMs from concentrating on two hosts, and spread them across the cluster or place them in a dedicated host group. Apply CPU and memory reservations or limits where the platform supports them, and monitor per-VM steal time, ready time, and host contention rather than only average utilization. If the workload is genuinely latency-sensitive, separate it onto dedicated hosts so the blast radius is bounded. Quotas and placement controls should be designed together: a tenant that is allowed 600 vCPU but pinned to two hosts can still create a local hotspot. Document the escalation path when a project approaches its quota so the fix is a reviewed capacity decision, not an emergency override.