Cross-Cloud Replication Calculator

steady state = changed GB × source egress + returned GB × destination egress + seeded GB × destination storage rate + requests ÷ 1,000 × request price; seed = dataset GB × compression factor × source egress rate. Cross-cloud replication pays egress at both ends, because the outbound copy leaves the source cloud and every verification read, restore or failback leaves the destination cloud at that provider's rate. On top of the wire cost you keep two copies of the data, so the destination storage line never goes away, and object-level replication generates a request charge per object that matters once the object count is in the millions.

Teams budget cross-cloud replication as a storage cost and discover it is mostly a network cost, and the seed transfer alone can exceed a year of steady-state spend. Rates vary sharply by provider pair and region, so price the specific route on both providers' calculators before you commit to the design.

This calculator takes 10 inputs: Dataset to seed, Daily change shipped, Compression and deduplication saving, Egress rate leaving the source cloud, Egress rate leaving the destination cloud, Share of changed data that flows back, Storage rate in the destination cloud, API requests per month, Request price, Months to amortise the seed transfer. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Often yes above a few tens of terabytes a month. A private interconnect or cloud exchange port replaces the per-GB internet egress rate with a port fee plus a much lower metered rate, and the crossover point is usually where sustained monthly transfer makes the fixed port cost worth committing to.