Japanese servers, due to their proximity to mainland China and relatively stable network quality, have long been the preferred choice for many businesses and individuals. However, many users encounter a thorny issue during their use: slow upload speeds. This issue not only affects file transfer efficiency but also slows data synchronization and backup processes, making it particularly challenging for businesses that rely on real-time data transmission. Tackling slow upload speeds on Japanese servers requires addressing multiple aspects, including network paths, hardware configuration, carrier policies, and software optimization.
Ⅰ. Identifying the Cause of Slow Upload Speeds
Before addressing the issue, it's crucial to identify the cause of slow upload speeds. Common contributing factors include:
Network Link Limitations: Japanese data centers offer varying bandwidth types, such as shared and dedicated bandwidth, resulting in significant performance differences. Low-cost shared links can be impacted by other users during peak hours.
International Outbound Congestion: Although Japan is relatively close to China, using standard international links can result in data packet congestion during peak hours, especially if the return path isn't optimized.
Insufficient local network upload capacity: Domestic broadband operators generally impose significant restrictions on uplink bandwidth. For example, a 100Mbps home broadband connection may only have an uplink of around 20Mbps, limiting data uploads from local servers to Japanese servers.
Server hardware bottlenecks: Insufficient CPU, memory, or hard drive performance on Japanese servers can also indirectly affect upload speeds, especially when processing large files.
Improper TCP/IP protocol parameters: Unoptimized server network parameters, such as a small TCP window size and delayed ACKs, can reduce long-distance transmission efficiency.
Improper software transmission methods: Some FTP clients or HTTP upload methods do not enable multi-threaded transmission, which can amplify latency and impact single-threaded transmission speeds.
II. Optimizing Network Connections and Bandwidth
1. Selecting High-Quality Connections
Japanese server connections include standard international connections, CN2 GIA, CN2 GT, and BGP multi-line connections.
CN2 GIA: Both outbound and return routes utilize high-quality connections, offering stable latency, low packet loss, and guaranteed upload speeds.
CN2 GT: Costs are lower than GIA, but there may be slight fluctuations during peak hours.
BGP Multi-Line: Suitable for users accessing diverse regions, automatically selecting the optimal backhaul.
If your upload traffic is primarily from mainland China, we recommend choosing CN2 GIA or Japanese servers with optimized routes directly connected to mainland China.
2. Prioritize Dedicated Bandwidth
Dedicated bandwidth is unaffected by other users, ensuring stable throughput regardless of peak or trough traffic. If your budget allows, consider a dedicated 10M/20M/50M or higher bandwidth plan to avoid resource competition on shared lines.
Ⅲ. Improving Local Network Uplink Capacity
Even if the Japanese server has sufficient bandwidth, insufficient local uplink bandwidth will still result in bottlenecks.
Upgrading your broadband plan: Upgrading from 100M to 500M or 1000M fiber can significantly improve uplink speeds.
Changing your carrier: Some carriers offer faster outbound links to Japan, so you can compare upload speeds on different carriers. Direct Fiber/Leased Line: For enterprise users, consider applying for an international leased line or IPLC (International Private Line) to bypass public network congestion.
IV. Adjusting Server Network Parameters
The default network parameters of Japanese server operating systems are typically optimized for local networks and are not suitable for long-distance, cross-border transmissions. Targeted adjustments can be made:
Increase the TCP window size by modifying parameters such as net.core.wmem_max and net.core.rmem_max in /etc/sysctl.conf to improve long-distance transmission capabilities.
Enable the BBR congestion control algorithm (on Linux servers). BBR can better utilize bandwidth and reduce speed drops under high latency.
Disable unnecessary delayed ACKs and adjust parameters such as tcp_delack_min to reduce ACK delays.
V. Optimize File Transfer Methods
Use multithreaded/segmented transfers, such as using a multithreaded FTP client like lftp or FileZilla, or using segmented transfer tools like aria2 or rclone.
Compressing files before uploading, or bundling multiple small files into a .zip or .tar.gz file for transmission, can reduce TCP connection overhead.
Choose an efficient protocol:
SCP/SFTP: Suitable for secure transmission, but limited by single-threaded speed.
Rsync: Suitable for incremental transmission, avoiding repeated uploads of the same content.
HTTP/HTTPS + multi-part upload: Suitable for integration with object storage.
Slow upload speeds on Japanese servers aren't caused by a single factor; rather, they are influenced by multiple factors, including network connections, bandwidth configuration, local environment, and server parameters. To fully address this issue, comprehensive optimization of the entire process, from line selection to protocol optimization to transmission strategy, is essential. For users who frequently transfer large files across borders, it's important to plan bandwidth plans in advance, use high-quality lines, and adjust network parameters.
