Snapshot Growth Calculator
Forecast how an incremental snapshot chain grows as the protected volume itself grows month over month.
Inputs
Snapshot Footprint at the Horizon
1,206.8GiB
Snapshot Footprint Today
672.0GiB
Growth Multiple
1.80x today
Cost in the Final Month
$60.34
Cumulative Cost Over the Horizon
$561.56
Average Monthly Cost
$46.80
Step by step
Values used
Written data on the volume today = 400 GiB; Daily change rate = 2 %; Snapshot retention window = 35 days; Monthly growth of the written data = 5 %; Forecast horizon = 12 months; Snapshot price = 0.0500 USD per GB-month
Snapshot Growth
footprint(month m) = written GiB x (1 + monthly growth)^m x (1 + (retention days − 1) x daily change rate).
Snapshot Footprint at the Horizon
= 1,206.8 GiB
Snapshot Footprint Today
= 672.0 GiB
Growth Multiple
= 1.80 x today
Cost in the Final Month
= 60.34
Cumulative Cost Over the Horizon
= 561.56
Average Monthly Cost
= 46.80
How it works
A snapshot chain reaches a steady state where it holds one base copy plus one delta for every day still inside the retention window, so the footprint is the written data multiplied by a factor set by retention and change rate. Growing the source compounds that whole footprint, which is why a 5% monthly increase becomes roughly 1.8x in a year rather than 60%. The price is a user-supplied list price to confirm on the AWS EBS pricing page for your region. Snapshot spend is the line item that grows without anyone changing a setting, and seeing the compounding early is what justifies shortening the retention window before the bill forces it.
Formula
Snapshot Growth
footprint(month m) = written GiB x (1 + monthly growth)^m x (1 + (retention days − 1) x daily change rate).
- chain factor
- Multiplier the retention window adds on top of the base copy
- monthly growth
- Compound growth rate of the written data
Frequently Asked Questions
How is Snapshot Growth calculated?
footprint(month m) = written GiB x (1 + monthly growth)^m x (1 + (retention days − 1) x daily change rate). A snapshot chain reaches a steady state where it holds one base copy plus one delta for every day still inside the retention window, so the footprint is the written data multiplied by a factor set by retention and change rate. Growing the source compounds that whole footprint, which is why a 5% monthly increase becomes roughly 1.8x in a year rather than 60%. The price is a user-supplied list price to confirm on the AWS EBS pricing page for your region.
Why does Snapshot Growth matter?
Snapshot spend is the line item that grows without anyone changing a setting, and seeing the compounding early is what justifies shortening the retention window before the bill forces it.
What values do I need to enter?
This calculator takes 6 inputs: Written data on the volume today, Daily change rate, Snapshot retention window, Monthly growth of the written data, Forecast horizon, Snapshot price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
Does a longer retention window cost proportionally more?
No, less than proportionally. Extending retention adds one daily delta per extra day, not another full copy, so going from 7 to 35 days at a 2% change rate roughly grows the footprint from 1.12x to 1.68x the written data.