Hello, I recently moved a physical server into virtual one. After the switch, I noticed that copying files to the server via scp became a lot slower. Usually I got speeds ~5000kb/s, but now it starts fast, however speed soon falls and sets stable at ~200kb/s.
After some investigation, I noticed the problem is exclusive to IPv6. I've got native IPv6 connection at client side and gre-tunneled connection at server side, however the tunnel endpoint is on the border router and not on the host nor guest - so to them it "seems native" (apart from obvious MTU issues). If I scp files over IPv4 or IPv6 to the host machine everything is ok. If I scp files over IPv4 to the guest machine everything is still ok. However when I scp large file to the guest over IPv6, I'm starting to get random TCP Dup ACKs from the guest and retransmissions from the client side, which are causing the slowdowns. Only sending data to the guest seems to be affected (and only via IPv6), receiving data from guest seems to be OK. I even tried copying files directly from host to guest and problem still persists, so it should be easily reproducible - you can simply assign neighbouring IPv6 addresses to host and guest and use scp to copy some large file from one to another. Here is typical wireshark output: TCP [TCP Dup ACK 1092#1] 22 > 40245 [ACK] Seq=8625 Ack=724417 Win=1188 Len=0 TSval=68312141 TSecr=92289699 SLE=727233 SRE=728641 TCP [TCP Dup ACK 1092#2] 22 > 40245 [ACK] Seq=8625 Ack=724417 Win=1188 Len=0 TSval=68312141 TSecr=92289699 SLE=727233 SRE=730049 TCP [TCP Dup ACK 1092#3] 22 > 40245 [ACK] Seq=8625 Ack=724417 Win=1188 Len=0 TSval=68312141 TSecr=92289699 SLE=727233 SRE=731457 SSH [TCP Fast Retransmission] Encrypted request packet len=1408 SSH [TCP Retransmission] Encrypted request packet len=1408 I also see Out-Of-Order from time to time: SSH [TCP Out-Of-Order] Encrypted request packet len=1408 All three machines (client, host, guest) are using Slackware-based distro with kernel-3.0.4. I just confirmed the issue with latest VirtualBox 4.1.4 r74291. Host machine has Intel 82575EB NIC chipset (igb driver); guest machine has Intel PRO/1000 MT Desktop adapter selected in bridge mode. If you need any more info just ask. I can also provide you tcpdump capture privately. -- Miha ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2dcopy2 _______________________________________________ VBox-users-community mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/vbox-users-community
