Large SFTP uploads become extremely slow when nearly finished

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wrecclesham
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Large SFTP uploads become extremely slow when nearly finished

I'm uploading folders containing a small number of large video files to a remote server.

My speedtest.net results show that my effective internet speed over WiFi is 600 Mbps down, 100 Mbps up.

My uploads using WinSCP start at a fairly decent 80 Mbps but, when they are nearly complete, the upload speed drops to around 1 Mbps. Interestingly, while WinSCP is struggling to upload files, a speedtest.net test will still give full download and upload speeds, so other applications are not experiencing slow connectivity - just WinSCP.

I've tried three things and have identified the step required to get my uploads back to normal:

- pause WinSCP upload + resume uploads in WinSCP = no improvement
- pause WinSCP upload + disconnect from WiFi/reconnect + resume upload = no improvement
- pause WinSCP upload + DISABLE WiFi NIC/re-enable WiFi NIC + resume upload = upload returns to full speed (approximately 10x faster).

Any idea why I'm seeing slow uploads towards the end of WinSCP transfers, which can only be resolved by disabling then re-enabling my NIC?

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martin
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Re: Large SFTP uploads become extremely slow when nearly finished

Please attach a full session log file on level Debug 1 showing the problem (using the latest version of WinSCP).

To generate the session log file, enable logging, log in to your server and do the operation and only the operation that causes the error. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.

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