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We're trying to optimise our network transfer rate from the client PCs to the file server, but having no luck.

If I run an iperf test between a client PC (Windows XP) and our server (Linux) with a large TCP window size (the default is 8kb) I can get 60 Mbps. But when I run an SMB transfer speed test all I get is around 35 Mbps. When I run an FTP transfer speed test all I get is around 32 Mbps.

I thought this was to do with the TCP window size, but I have now increased that to 256960 and it made no difference at all.

Any ideas what I'm doing wrong? Or is 35 Mbps all I should expect?


share|improve this question
What is the transfer rate of your hard drives? Can you pull data off the drives faster then 35Mbps? Can you save data on your client faster then 35Mbps? Iperf is a pure network test. FTP/SMB is going to be limited by the I/O capabilities of the storage. – Zoredache Mar 13 '10 at 10:38
Huh, I cant believe that didn't even occur to me, think that might be exactly the problem. I guess the network is transferring perfectly well then. – Jack Sleight Mar 13 '10 at 10:50
Did you ever verify if the drives were the bottleneck? – Nathan V Nov 29 '12 at 5:31

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