DCI Bandwidth Calculator
Size a data centre interconnect from daily change rate, replication window, RPO and distance latency.
Inputs
DCI Bandwidth Required
311.11Mbps
Sustained Rate
155.56Mbps
Rate Needed to Hold the RPO
51.85Mbps
Round-trip Latency
6.00ms
Replication Mode Feasible
Synchronous possible but latency-sensitive
Step by step
Values used
Daily data change = 800 GB; Replication window = 8 hours; Recovery point objective = 15 minutes; Reduction from compression and dedup = 30 %; Peak-to-average factor = 2 x; Distance between sites = 600 km
DCI Bandwidth
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01.
DCI Bandwidth Required
= 311.11 Mbps
Sustained Rate
= 155.56 Mbps
Rate Needed to Hold the RPO
= 51.85 Mbps
Round-trip Latency
= 6.00 ms
Replication Mode Feasible
= Synchronous possible but latency-sensitive
How it works
Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km. DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
Formula
DCI Bandwidth
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01.
- change GB × 8000
- Gigabytes converted to megabits
- 0.01 ms/km
- Round-trip fibre delay — 5 µs per km each way
Frequently Asked Questions
How is DCI Bandwidth calculated?
sustained Mbps = change GB × 8000 ÷ window seconds × (1 − reduction); required = sustained × peak factor; RTT ms ≈ distance km × 0.01. Replication bandwidth is the changed data divided by the window it must fit into, reduced by compression and then inflated by how peaky the change rate is. Distance sets a floor on latency that no amount of bandwidth fixes, which is what rules synchronous replication in or out beyond roughly 100 km.
Why does DCI Bandwidth matter?
DCI circuits are the most expensive links a business buys, and RPO commitments are contractual — both depend on this figure being right rather than optimistic.
What values do I need to enter?
This calculator takes 6 inputs: Daily data change, Replication window, Recovery point objective, Reduction from compression and dedup, Peak-to-average factor, Distance between sites. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.