Calculator Inputs
Use the fields below to estimate replica storage, sync traffic, transfer time, and recovery-point feasibility.
Example Data Table
Sample engineering replication plan using the default values in this file.
| Parameter | Example Value | Estimated Output |
|---|---|---|
| Source dataset | 12 TB | Primary source remains 12 TB |
| Daily change rate | 4% | About 491.520 GB changed daily |
| Replica copies | 2 | Two replica targets receive synchronized changes |
| Reduction factor | 1.8 | Replica payload and retained deltas shrink materially |
| Bandwidth and usable share | 850 Mbps and 75% | Effective payload about 569.20 Mbps |
| Sync and RPO | 30 minutes and 45 minutes | Estimated effective RPO about 31.36 minutes |
| Total footprint | With 7-day snapshots | About 29.066 TB overall |
| Monthly traffic | Thirty-day estimate | About 15.996 TB transferred |
Formula Used
Source Size (GB) = Entered Size × Unit Factor
Daily Changed Data = Source Size (GB) × Daily Change Rate ÷ 100
Per Sync Change = Daily Changed Data × Sync Interval ÷ 1440
Compressed Sync Payload = Per Sync Change ÷ Reduction Factor
Payload Bandwidth = Raw Link × Usable Share ÷ (1 + Protocol Overhead)
Transfer Time (minutes) = Compressed Sync Payload × 8192 ÷ Payload Mbps ÷ 60
Effective RPO = Sync Interval + Transfer Time
Daily Traffic = Daily Changed Data ÷ Reduction Factor × Replica Copies
Total Footprint = Source + Replica Base Storage + Snapshot Delta Storage
Assumption: the reduction factor applies to replica payload and stored replica blocks. The primary source remains unchanged.
How to Use This Calculator
FAQs
1) What does the reduction factor represent?
It represents data reduction from compression or deduplication. A value of 1.8 means replica payload and retained delta blocks are reduced by that factor before storage and transfer calculations.
2) Why is effective RPO larger than the sync interval?
Because data must first wait for the next sync window, then traverse the network. The calculator adds sync interval and transfer time to estimate total recovery-point exposure.
3) Does more replica copies increase traffic?
Yes. Each extra replica target receives the changed data stream. That raises both daily transfer volume and long-term stored replica capacity.
4) Why keep snapshot retention in the model?
Snapshot retention stores recent changed blocks for rollback and point-in-time recovery. It often adds meaningful capacity even when the base replica is already compressed.
5) What happens when the sync interval exceeds the RPO target?
The design becomes infeasible before network transfer is even considered. The calculator flags that condition and cannot produce a valid required bandwidth for that target.
6) Is raw link bandwidth the same as usable bandwidth?
No. Raw link bandwidth is the nominal circuit rate. Usable bandwidth is the share available to replication after contention, reserved traffic, and operational throttling.
7) Can this calculator support first-time seed planning?
Yes. It estimates full seed time using the selected source size, reduction factor, and effective payload bandwidth, which helps evaluate initial cutover feasibility.
8) Should annual growth always be included?
Yes for planning. Growth shifts both daily change volume and long-term footprint. Ignoring it can undersize bandwidth, storage, and recovery readiness within a year.