Cloud cost
Cluster idle
Node capacity that's schedulable but was never even requested by any pod: a bin-packing and autoscaling problem, not a request-sizing one.
Last updated
Definition
Cluster idle is the gap between what a cluster's nodes can schedule (allocatable capacity) and what's been requested by any pod. It's provisioned, billed, and sitting empty; no workload asked for it at all. That makes it a different failure mode from workload idle (below): the fix is autoscaler tuning, tighter bin-packing, and matching node shape to the workload, not resizing any single pod's request.
Datadog's State of Cloud Costs research puts roughly 54 of the 83 idle percentage points it measures in container spend into this bucket, the larger of the two idle categories on the clusters it sampled.
Where it shows up
Cluster idle shows up as the gap between a node's allocatable capacity and the sum of every pod's requests scheduled onto it, visible in a cluster's resource-usage dashboard or in the Allocated resources section of the kubectl describe node output for that same node, summed across the whole node pool.
What makes it expensive
A common expensive habit is treating cluster idle as a request-sizing problem and tuning individual pods, when the real lever is autoscaler configuration and bin packing across the whole node pool. One node with a wide allocated-versus-allocatable gap is noise. The same gap across most of the pool is a scheduling decision nobody made on purpose.
Related
More in Cloud cost
- Committed use discount (CUD)
- Reserved instance (RI)
- Savings plan (SP)
- On-demand vs. spot instances
- Data egress
- Amortized, blended, and unblended cost
- Billed vs. effective vs. list vs. contracted cost
- Rightsizing
- Idle and orphaned resources
- Storage class
- Lifecycle policy
- Incremental snapshot
- Allocatable capacity
- Requests vs. limits
- Workload idle
- Bin packing
- Cost allocation tags
- Tag coverage
- Unallocated spend
- Showback vs. chargeback
- Unit economics
- RI/SP coverage and utilization
- Observability tax
- Metric cardinality
- High-water-mark billing
- Log ingest vs. index
- Snowflake credit
- Auto-suspend / resume minimum
- BigQuery slot
- Bytes scanned & partition pruning
- Time Travel & Fail-safe
The meter you don't watch still grows.
Waste rarely hides in the service you check every week. CostMon watches every meter on your stack, including the ones you forgot were running.