Maximizing SFTP Performance

In general, SFTP has bad performance characteristics due to limitations in the design of the protocol. The steps below will help you get the most out of SFTP.

Maximize the Buffer Size (Data Chunk Size) in your SFTP Client

Most SFTP clients send data in chunks of 32 kilobytes. This is a ridiculously low size for today's internet.

We recommend increasing this size by 4-32x in your client. Unfortunately, this process requires some trial and error to perfectly optimize in SFTP. Other protocols handle this process much more automatically.

If you are using the command line sftp tool, you can set the buffer size using the -B option: sftp -B 128000

If you are using any other client, look for settings related to buffer size or data chunk size and crank them up.

Use Many Parallel Connections

Set the number of simultaneous connections to 10-25 or the maximum supported by your SFTP app.

To increase the number of simultaneous connections in FileZilla, go to Edit > Settings > Transfers and increase the Maximum simultaneous transfers setting to 10.

To increase the number of simultaneous connections in Cyberduck, first go to Edit > Preferences > Transfers and set Transfer Files to "Open multiple connections".

Then, go to to Window > Transfers and increase the counter in the lower right to the maximum.

Increasing the number of simultaneous connections will help when uploading multiple files at the same time but will not have any effect when uploading a single file.

Minimize Network Latency

Network latency is measured as the round-trip delay between sending data across a network and receiving a reply that the data was received. Higher latency, also known as "lag", can be caused by:

  • physical limitations, such as your physical network connection.

  • how much data is currently saturating your network connection.

  • the network distance between you and your destination.

  • network tools and software that regulate or restrict bandwidth usage.

Network latency has a large impact on SFTP performance. Whenever possible, use the best physical network available to you and try and achieve the shortest network distance possible.

Use the best physical network available to you

For example, choose a physical ethernet connection over a Wi-Fi connection.

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