James G. Sack (jim) wrote:
Gus Wirth wrote:
Andrew Lentvorski wrote:
Gus Wirth wrote:
If I do an NFS mount and copy a large file from the server to
/dev/null on the client or if I scp a file between the server and
client I get pretty much the same results, about 11MB (that's bytes)
per second. This is only about 10% better than 100baseT ethernet. I
know from previous experiments that my hard drives and general system
throughput can handle about 25MB/sec.
If you are seeing 10 MibiBytes per second on a 100baseT, you
effectively have no network traffic on it. Must be nice. That's one
reason why you are seeing practically no increase.
This is my home network, with currently only two machines running. But I
would have expected to about double my transfer speed based on my
current system capabilities.
Second, I think you need to bump the default TCP packet size. On a
network that small, the TCP window is probably filling and throttling
the transfer rate.
Make sure your systems are sending 9000+ byte packets rather than just
1500+ byte packets.
OK, off to the man pages to figure out how to do that.
maybe:
ifconfig eth0 mtu 9000
That's it. Unfortunately, it breaks networking. Or more specifically, it
breaks when network packets exceed 1500 bytes. Setting the MTU of either
machine causes something to choke and the connection dies.
For example, I set MTU=9000 on both machines. I monitor the connection
on the server with Ethereal. I start a scp operation from the server to
the client. The initial exchange and negotiation of the ssh keys goes
fine. However, as soon as a data packet gets transmitted that's bigger
than 1500 bytes, the transmit queue starts to back up and I stop getting
any replies from the client. It's really weird and I'm not sure what I
should be looking at. I'm thinking I should get a gigabit crossover
cable (is there such a thing?) and try without the switch to eliminate
that as a potential problem.
On the other hand, I now know about the ip command, sysctl, ethtool, and
a bunch of stuff in /proc/sys/net, none of which fixes my problem.
Gus
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