WinSCP Upload transfer speed limit/cap.

Problem: Same slow maximum limit/cap for any files.

WinSCP Version: 5.5.6 (Build 4746)

File sizes: ~4GB , ~300MB
File types: .7z , .mkv

Physical line: Gigabit Ethernet

[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 850 MBytes 712 Mbits/sec

Microsoft Windows: Windows 7 Ultimate x64
Transfer protocol: SFTP-3
interface style: Commander Interface

Slow WinSCP Upload transfer speed: 4.780 KB/s

Precise steps: Drag and drop test files(see earlier info) from a fast SSD on the client desktop to server(typical HDD) by dragging from desktop to server location in GUI window.

Additional details:
.

Thanks for your report.
What are you results using other SFTP clients (FileZilla, PSFTP)?

File Size: 1,457,835,581 Bytes.
Type: .mkv

Method: FileZilla(SFTP)
Upload speed: 8.5 MB/s
Download speed: 26.21 MB/s

Method: WinSCP(SFTP-3)
Upload speed: 4,958 KB/s
Download speed: 19 MB/s

Can you try 5.6.4 RC and execute it from a command-line like this?
Please attach the log here.

Upload speed: ~5,150 KB/s
Download Speed: ~19,300 KB/s

<invalid hyperlink removed by admin>

Sorry for delay. I have implemented yet another improvement:
Issue 1273 – Increase size of connection receiving buffer
I have sent you an email with a development version of WinSCP to address you have used to register on this forum.

Same. Download speed got even worse... got down to 11.5 MB/s

Thanks for the test.
Can you please repeat the test with 5.6.4 RC to verify there are no external causes for the decrease?

Ah, please, ignore the 11.5 MB/s download "downgrade", it happened because the connection to my server somehow got dumbed down to 100Mbs instead of the usual 1000Mbs.

After renegotiation to 1000Mbs, the download is back to around 19 MBs (Kind of also get the feeling the download is capped).

Regardless, the upload should have been more than 5MBs on either connection mode, so the problem with upload remains the same.

I have sent you an email with some binaries for testing. Thanks!

Replied with an email containing details of testing binaries.

Hey Martin.

I have tried 5.7. Unfortunately it gives the same speed as 5.6.5 RC.

Perhaps you could include a x64 version so we could confirm those assumptions?

RandomInternetGuy wrote:

Perhaps you could include a x64 version so we could confirm those assumptions?

It's not easy to make 64-bit version of WinSCP. We definitely aim for that, but it will take time.