Slow download speed when saving to network drive

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fletchowns
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Slow download speed when saving to network drive

Client side is Windows 10 running WinSCP 5.17.10. Server side is Debian 10. I've got a network drive mapped in Windows and noticed that when downloading to the network drive (Samba), speed tops out at 5 MB/s. However, if I download to SSD instead, I'm getting 50 MB/s.

As a quick sanity check I tried Windows file copy from the SSD to the network drive and it saturates the 1 Gbps link @ 107 MB/s.

I tried toggling "Optimize connection buffer size", and "Enable compression" but didn't see any improvement.

I tried the same test with FileZilla and got 50MB/s whether it's downloading to the SSD or to the network drive. However, I'd prefer to use WinSCP because of the nice scripting capabilities.

Is there any way I can improve the transfer speed when saving to a networked drive? Thanks!

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martin
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Re: Slow download speed when saving to network drive

Please post session log files both for the download to SSD and the network drive.

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fletchowns
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Re: Slow download speed when saving to network drive

Attached a session log of first downloading 1GB file to Desktop folder (SSD) at 30 MB/s and then downloading to Z:\ (network drive) at about 5 MB/s. Thanks for taking a look!
  • winscp-ssd-vs-network_drive.log (17.39 KB, Private file)

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fletchowns
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Attached the log repeating the same steps but with Debug 1 logging. Thanks again!
  • winscp-ssd-vs-network_drive-debug1.zip (2.65 MB, Private file)

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fletchowns

Thanks Martin! That seems to have helped. Transfer speed increased from 5 MB/s to 26 MB/s when downloading a file over SFTP to the Samba share. Seems like something still isn't quite right though, because downloading to SSD is still much faster, consistently getting 90MB/s with that test now after many test runs.

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fletchowns

Thanks Martin! I'll play around with different values and see how it goes. What does SFTPDownloadQueue do exactly? What's the default value? What's considered a really high value?

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martin
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It controls for how much data will WinSCP ask the server for before waiting for a response. With high latency connections (in your case the slow network drive has the same effect as a high latency), higher value is needed to saturate the bandwidth.

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