NetFlow Storage Calculator

Size NetFlow collector storage and export bandwidth from flow rate, sampling and retention.

About NetFlow Storage Calculator

Flow export volume is the flow rate times the record size; sampling divides the rate directly, which is why 1-in-1000 sampling is the standard way to make high-rate interfaces affordable to monitor. Retention and compression scale the stored figure. Flow data grows faster than any other telemetry — a busy edge router at 20,000 flows per second produces around 95 GB a day unsampled, which decides whether you need sampling or a bigger array.

Formulas

NetFlow Storage

storage = flows/s ÷ sampling × 86400 × record bytes × retention ÷ compression, with NetFlow v9 records running 40–70 bytes each.

record bytes: Size of one exported flow record — 40 to 70 bytes for NetFlow v9
sampling: 1-in-N packet or flow sampling divisor
compression: Collector compression of stored records

Exporter to collector bandwidth

export bandwidth = exported flows/s × record bytes × 8

exported flows/s: Flow rate after sampling

Worked example

With the default values below, NetFlow Storage Calculator returns Retained Storage Required of 2 TiB. Change any input above and every figure here is recalculated in your browser.

Inputs used

Flows per secondminimum 0.1 flows/s: 20,000 flows/s
Bytes per flow recordaccepts 20–200 bytes: 55 bytes
Sampling rate (1 in N)minimum 1 N: 1 N
Retention periodminimum 1 days: 90 days
Compression ratioaccepts 1–30 ×: 4 ×

Results

Retained Storage Required: 2 TiB
Raw Volume Per Day: 89 GiB
Flow Records Per Day: 1,728,000,000
Export Bandwidth: 8.80 Mbit/s
Retained Storage Required: 1.945 TB

Step by step

1Values used
2NetFlow Storage
3Exporter to collector bandwidth
4Retained Storage Required= 2,138,400,000,000
5Raw Volume Per Day= 95,040,000,000
6Flow Records Per Day= 1,728,000,000
7Export Bandwidth= 8.80 Mbit/s
8Retained Storage Required= 1.945 TB

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is NetFlow Storage calculated?

storage = flows/s ÷ sampling × 86400 × record bytes × retention ÷ compression, with NetFlow v9 records running 40–70 bytes each. Flow export volume is the flow rate times the record size; sampling divides the rate directly, which is why 1-in-1000 sampling is the standard way to make high-rate interfaces affordable to monitor. Retention and compression scale the stored figure.

Why does NetFlow Storage matter?

Flow data grows faster than any other telemetry — a busy edge router at 20,000 flows per second produces around 95 GB a day unsampled, which decides whether you need sampling or a bigger array.

What values do I need to enter?

This calculator takes 5 inputs: Flows per second, Bytes per flow record, Sampling rate (1 in N), Retention period, Compression ratio. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.