Calculator Inputs
Plotly Graph
The chart shows how each component contributes to total memory demand.
Formula Used
Total per-record bytes = Average RRset Bytes + Average Key Bytes + Metadata Bytes
Raw Cache Memory = Cached Records × Total Per-record Bytes
Index Memory = Raw Cache Memory × (Index Overhead ÷ 100)
Cache After Features = (Raw Cache Memory + Index Memory) × Feature Multiplier
Worker Memory = Worker Threads × Per Thread Buffer KB × 1024
Client Memory = Concurrent Clients × Per Client State KB × 1024
Recommended Memory = (Cache After Features + Worker Memory + Client Memory) × (1 + Safety Margin ÷ 100)
Feature multiplier values in this calculator:
- DNSSEC adds 30%.
- EDNS Client Subnet adds 15%.
- Prefetch adds 10%.
- Serve Stale adds 8%.
How to Use This Calculator
- Enter the number of cached DNS records you expect.
- Set average bytes for payload, key, and metadata.
- Choose index overhead for your resolver structure.
- Enable optional features matching your deployment.
- Add worker thread and buffer settings.
- Enter expected client concurrency and query state size.
- Apply a safety margin for bursts and growth.
- Press Calculate Memory to view the estimate.
- Review the breakdown table and the graph.
- Download the report as CSV or PDF.
Example Data Table
| Profile | Cached Records | Avg RRset | Workers | Feature Multiplier | Recommended Memory |
|---|---|---|---|---|---|
| Small Edge Resolver | 120,000 | 300 B | 4 | 1.10× | 80.39 MB |
| Regional ISP Resolver | 500,000 | 420 B | 8 | 1.48× | 633.80 MB |
| Large Public Resolver | 2,000,000 | 520 B | 24 | 1.63× | 3.72 GB |
These profiles are examples. Real memory use depends on resolver design, allocator behavior, TTL churn, cache eviction, transport mix, and implementation details.
FAQs
1) What does this calculator estimate?
It estimates memory for a DNS resolver cache, index structures, worker buffers, client state, optional features, and extra safety capacity.
2) Why are key bytes and metadata separated?
Resolver entries usually store payload data, lookup keys, and internal bookkeeping separately. Splitting them gives a more realistic sizing model.
3) Does DNSSEC really increase memory usage?
Yes. DNSSEC often adds signatures, larger answers, and validation state. That typically increases cache pressure and operational memory needs.
4) What changes when ECS is enabled?
EDNS Client Subnet can create more cache variation. More variations often mean more entries, larger indexes, and higher memory demand.
5) Why include worker thread buffers?
Even efficient resolvers reserve memory for thread-local buffers, sockets, and parsing work. Those allocations matter under sustained load.
6) Why should I add a safety margin?
Traffic spikes, feature growth, longer responses, and fragmentation can all push memory higher. A margin helps absorb unexpected demand.
7) Can I use this for different resolver software?
Yes. It is implementation-agnostic. Adjust the average bytes and overhead settings to match your resolver’s observed behavior.
8) Is this an exact production memory figure?
No. It is a planning estimate. Validate it against real metrics, memory profiling, and live traffic patterns before deployment.