sshfs over wireless slows to a crawl

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Joined: Tue Oct 06, 2009 6:55 am

sshfs over wireless slows to a crawl

Postby jwj » Fri Oct 23, 2009 2:07 pm

I have a funny problem using sshfs over wireless --- when copying (i.e. writing) large files, it initially runs at a very reasonable 1000-2000 kB/s (with the occasional drop, it is wireless, after all), but after a while (can be anything from 5 to maybe 60 sec) it drops down to about 60-70 kB/s and remains there.

When I do the same thing (as in same files, directories, machines, sshfs etc.) over a wired connection, it keeps ticking away for hours at a steady 11000-12000 KB/s (that's over a 100 Mb/s connection, so it is pretty much what one would expect).

Also, the wireless connection itself seems to work fairly reliably for anything other than sshfs --- including stuff like bittorrent etc. That makes me wonder whether (1) there is some known problem in the interaction between wireless networking and sshfs, and whether (2) there are some sshfs (or other) settings that would help me work around it. I have played with the cache sizes and read and write request sizes etc., without effect.

This is on a T42p ThinkPad running Mint 7 Xfce CE, and lspci yields
02:02.0 Ethernet controller: Atheros Communications Inc. AR5212 802.11abg NIC (rev 01)


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Re: sshfs over wireless slows to a crawl

Postby grimdestripador » Fri Oct 23, 2009 3:13 pm

I propose that your periodically check the connection speed of the wireless signal. Sometimes when transferring a lot of packets, it negotiates a slow speed because it detects data loss that would be otherwise ignored in packet burst. ssh is encrypted and is difficult to have an accurate checksum, more than a bunch of padded zeros on a text file. I believe you can lock the negotiation speed on the network cards. Also bit torrent is many simultaneous connection.

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