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Slow SCP
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Slow SCP

plumbergplumberg Veteran

Hi,
When I am transferring one file over SCP from Server A to Server B, it happens fast (average 10MBPS). However, transferring from Server B to Server A via SCP is super slow; 500 kbps max.

I have tried the transfers at different times of the day. Still, same result.

How can I troubleshoot the one-way slowness? Both run Linux. Different network providers.

Thanks!

Comments

  • AnthonySmithAnthonySmith Member, Patron Provider

    Soes the slowness persist to any destination when server B is the source or just to Server A?

    Is the disk busy in terms of reads on Server B or is Server A busy in terms of disk writes?

  • My money is on crappy peering.

  • @AnthonySmith said:
    Soes the slowness persist to any destination when server B is the source or just to Server A?

    Is the disk busy in terms of reads on Server B or is Server A busy in terms of disk writes?

    I even tried with a different provider... Incoming to Server A is slow from another provider also. But, outgoing is fast.

    Server A (receiver of slow files) is completely idle. Its a new server setup.

    All providers are saying, I dont see any problems.

  • AnthonySmithAnthonySmith Member, Patron Provider

    can you boot server A in to recovery mode and try it just to 100% rule anything out on the server (expect the same result).

    After that gather tracert info both ways, ask the DC for a local test file (which will probably work fast) and then ask them why they think that 500kbps is not a problem.

    It might also be worth testing things using wget to back things up.

  • @AnthonySmith said:We
    can you boot server A in to recovery mode and try it just to 100% rule anything out on the server (expect the same result).

    After that gather tracert info both ways, ask the DC for a local test file (which will probably work fast) and then ask them why they think that 500kbps is not a problem.

    It might also be worth testing things using wget to back things up.

    So I submitted a MTR to and fro. Mid way one of the hops has some packet loss. Provider said since final hop had no loss nothing seems to be wrong. Hence I am at a loss on how to find out the root cause of the problem and get it resolved.

    Thanks.

  • MikeAMikeA Member, Patron Provider

    It's just with scp? Try rsync to see if the same happens if you don't want to test in rescue mode.

  • @MikeA said:
    It's just with scp? Try rsync to see if the same happens if you don't want to test in rescue mode.

    Hmm. I'll try. Thanks

  • IkoulaIkoula Member, Host Rep
    edited April 2017

    Would you mind show us interfaces full ip configuration ?

  • pbgbenpbgben Member, Host Rep

    Using winscp? Its a pile of shithouse. Use cyberduck

  • @pbgben said:
    Using winscp? Its a pile of shithouse. Use cyberduck

    I am using command line scp. Both are Linux

  • @Ikoula said:
    Would you mind show us interfaces full ip configuration ?

    How?

  • AnthonySmithAnthonySmith Member, Patron Provider

    no offence but troubleshooting this sort of issue requires a degree of understanding, that degree far exceeds knowing how to show your interface configuration, or more to the point, even the knowledge that you could just google it.

    I think you are best off just paying your DC staff to investigate for you or moving your server.

  • @AnthonySmith said:

    no offence but troubleshooting this sort of issue requires a degree of understanding, that degree far exceeds knowing how to show your interface configuration, or more to the point, even the knowledge that you could just google it.

    I think you are best off just paying your DC staff to investigate for you or moving your server.

    None taken. Is it just ifconfig op needed?

  • JarryJarry Member

    I'd check MSS/MTU setting on both servers and along the route (i.e. tracepath). This might be caused by packet fragmentation...

  • Also note that even then you might still not get an answer. I just moved 175 megabytes on a colocated server in Dallas to a colocated server in LA with both locations being colocated with the same company, and this transfer ran about 800 kilobytes a second.

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