How to Move 1,000 TB from Nanjing to Beijing in Under a Day

Network Transfer Estimates

Assume an enterprise‑grade dedicated data line with a raw capacity of 100 Gbps. Converting to bytes gives an ideal data rate of 100 Gbps ÷ 8 = 12.5 GB/s. Over one hour this yields 12.5 GB/s × 3600 s ≈ 45 000 GB (≈ 45 TB). To move 1 000 TB (≈ 1 PB) would therefore require 1 000 TB ÷ 45 TB ≈ 22.2 hours, i.e., roughly one day under perfect conditions. In practice, TCP/IP overhead, error‑correction, and typical utilization (70‑80 % of raw capacity) increase the time to about 25‑30 hours.

A 10 Gbps internet‑grade leased line provides a raw rate of 1.25 GB/s, or about 4.5 TB per hour. Transferring 1 PB would take roughly 10 days in an ideal scenario; realistic throughput (≈ 60‑70 % of raw) pushes the duration to 12‑14 days.

Residential broadband (1 Gbps downstream, 300 Mbps upstream) caps upstream at ~37.5 MB/s, delivering only ~135 GB per hour. Moving 1 PB would therefore require > 7 000 hours, i.e., several months.

Dedicated lines are point‑to‑point services and are billed per month (e.g., ~35 W/month for 100 Gbps, ~54 W/month for 10 Gbps), making long‑duration bulk transfers financially prohibitive.

Human‑Courier (Physical Transport) Method

Transporting the data on portable storage devices (e.g., 16 TB hard‑disk drives) via high‑speed rail offers a dramatically higher effective bandwidth. To move 1 000 TB you need 1 000 TB ÷ 16 TB ≈ 63 drives. Loading these onto a high‑speed train (average speed ~300 km/h, distance Nanjing‑Beijing ≈ 1 200 km) results in a travel time of about 5 hours. Adding ~2 hours for local handling at each end yields a total door‑to‑door time of roughly 7 hours.

The effective bandwidth of this “sneakernet” can be estimated as:

Effective bandwidth = Total data / Transfer time
                     = 1 000 TB / 7 h
                     ≈ 143 TB/h ≈ 40 GB/s

This figure is comparable to, and in practice exceeds, the sustained throughput of a 100 Gbps line once protocol overhead and scheduling delays are considered.

Cost estimate (based on 2023 Chinese rail ticket prices): round‑trip train tickets for the cargo amount to 464 CNY × 2 = 928 CNY; adding taxi fares at origin and destination brings the total to roughly 1 100 CNY (≈ 150 USD). This is orders of magnitude cheaper than leasing a 100 Gbps line for a month, which can cost several hundred thousand yuan.

Key Takeaways

Raw network bandwidth calculations ignore protocol overhead, latency, and utilization limits; real‑world transfer times are longer.

High‑capacity dedicated lines are expensive; a month‑long lease can cost several hundred thousand yuan.

Physical transport of large data volumes (sneakernet) can achieve an effective bandwidth comparable to high‑speed links while costing a fraction of the price, provided the data does not require intermediate processing.

When planning bulk data migration, evaluate both network and physical options, considering total cost, required transfer window, and data‑security constraints.