Re: slow sftp/scp access despite fast network

On Tue, Nov 29, 2005 at 12:34:31AM +0000, Kris Harris wrote:
> on the system of interest (i.e. sftp localhost), I get like 10Mb/s, so the
> server doesn't seem pooched

Hopefully you meant 10MB/s? 10Mb/s is about 1MB/s, which I think
seems extraordinarily slow for transfers on the local machine... On
my laptop I get about 6.5MB/s for a 20MB file. Which still seems
rather slow to me, but it's more reasonable.

> the computer is actually the head node of a small cluster and I get the
> results:
> node2 to to master(gutowsky) via sftp: starts at 200 KB/s and ends on a
> cumulative rate of 100 KB/s, which is acceptable I suppose
> node2 to master(gutowsky) via iperf: 4.49 Mbits/sec (560 KB/s ?)

These are on the same LAN? These numbers sound horrible. On a
100Mb/s LAN, you should be able to achieve speeds of at least 4-5 MB/s
or so. Over my 802.11b network (11Mb/s) I can get speeds of up to
about 700KB/s. With a 100Mb/s LAN and no encryption/compression, you
should see speeds of around 8-9MB/s if your ethernet hardware doesn't
suck (and isn't misconfigured).

> (p.s., tried the usual net-problem charachters of switch, full/half duplex
> mode, and a different kernel module (but still 2.4 kernel))

Well, I definitely would have jumped on duplex being the issue... Did
you check carefully the connections on both the switch and the local
host to make sure there is no duplex mismatch? I've seen it happen
fairly often that the switch autonegotiates to 100Mb/Full but the host
autonegs to half duplex. Did you check the config on both ends
of the connection (switch and host, for sender and receiver)?

To check in Linux, you can use mii-tool or check the output of dmesg.
If you're using GB ethernet, some distros may not have a version of
mii-tool which reports the link status correctly.

Derek D. Martin
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