Replication Time
Calculate the time required to replicate data across storage nodes or sites.
About Replication Time
Replication time is the effective data volume (after compression reduces what actually needs to cross the wire) divided by the available link bandwidth converted from bits to bytes. WAN links are quoted in Mbps (megabits/sec) while data is measured in GB (gigabytes), so bandwidth must be divided by 8 to get MB/s before the comparison is meaningful — a common source of 8x errors when sizing replication or DR links.
Formula
Replication time
time = data_GB / (bandwidth_Mbps / 8) / compression_ratio
Worked example
With the default values below, Replication Time returns Estimated Replication Time of 2.28. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Data Size to Replicateminimum 0 GB
- 200 GB
- Link Bandwidthminimum 1 Mbps
- 100 Mbps
- Compression Ratiominimum 1
- 2
Results
- Estimated Replication Time
- 2.28 hrs
- Estimated Replication Time
- 136.5 min
- Effective Data After Compression
- 100.00 GB
- Link Bandwidth
- 12.50 MB/s
Step by step
- 1Values used
- 2Replication time
- 3Estimated Replication Time= 2.28 hrs
- 4Estimated Replication Time= 136.5 min
- 5Effective Data After Compression= 100.00 GB
- 6Link Bandwidth= 12.50 MB/s
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 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
Why divide bandwidth by 8?
Network bandwidth is conventionally quoted in bits per second (Mbps) but data volumes are measured in bytes (GB), and there are 8 bits per byte — so a 100 Mbps link provides roughly 12.5 MB/s of usable throughput, not 100 MB/s.
Does this account for replication overhead like checksums or retries?
No — this models ideal sustained throughput at the stated compression ratio. Real replication also has protocol overhead, retransmissions on lossy links, and often runs below the link's rated bandwidth due to latency (especially over long-distance WAN links where TCP window size can bottleneck throughput before bandwidth is the limit).
How much does compression actually help for replication?
It depends heavily on data type — already-compressed data (video, encrypted volumes) may see a ratio near 1, while text, logs, or database dumps often compress 2-4x, directly cutting replication time by the same factor since less data crosses the link.