50mb WAN link slow when transferring lots of files

[Andy White]

Hello,

We have had a 50mb fibre line put into a remote office, when we copy a large file of 2gb in either direction we get nearly 50mb constantly, if we copy small files equivalent to 2gb then traffic only hits only 30mb.  This is TCP traffic, why would the bandwidth utilisation be lower on a mulitple file transfer.  Is it something to do with the 3 way handshake or window size?  I want to see if the routers or switches can be tweaked.

Thanks

[CHAD REID]

Andy, that's an interesting question, and I don't have answer. But I would recommend trying the following, if possible, so you can determine the answer. Sniff the traffic somewhere on the source side to see what's going on. My gut is telling me that this likely a problem on either the source or destination computers where it's taking a long time to prepare large groups of smaller files for transmission. If that's the case, you should see long delays between the sending of each file.

We once had a similiar issue with a windows file server. The file system on the file server was having issues.

[dschlicht]

This is pretty typical to have slower transfer speeds when transferring lots of smaller files than fewer larger files. Rather than explaining here I will refer you to this link for a pretty good explanation: http://www.makeuseof.com/answers/transfer-times-small-files-slower-big-file/ this could very well be a contributing factor.

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[paolo bevilacqua]

As it was correctly answered above too. that is normal. In small files transmission TCP window doesn't have the time to adjus tto optimal, and there is more overhead.

[Jeff Van Houten]

You can also try to change the protocol you use to transfer the files. In my experience FTP is much more efficient than cifs/smb.

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