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FTP Transfer Slower when Physical Path is on a network share (UNC path)

phead_2 asked
Last Modified: 2012-05-09
FTP Server:

Windows Server 2008 (32 bit)
IIS FTP 7.5 for IIS 7.0 installed
FTP site setup using with user isolation, root directory hosted on a file share on a file server
FTP server and file server on GB ports, 5Mb internet connection (ethernet).

The transfer rate when downloading files is ~1/3 the rate it would be if the site's physical path is on the same machine the ftp server is running on. This goes for internal as well as external access.

When using the UNC path I get ~20MB/sec internally and ~100kb/sec over the internet (as fast it should be, we have a 5Mb internet connection, but I'm testing from a location with ~3Mb download speed).

If I reconfigure to use a local directory I get ~60MB/sec internally and ~300kb/sec over the internet.

Obiously I'm not really concerned about the internal speed either way, I need to recrtify the issue for internet downloads. Obviously bandwith is sufficient between the file server and the ftp server...

 It seems clear to me it is being limited at about 1/3 of the max available bandwidth from the client. I'm not aware of any setting that controls this, I've tried pretty much every iteration of setup combinations (including using other servers) to determine the issue only occurs when using the UNC path.

What is casuing the slow down? Using a local path isn;t going to work due to size of the directory...
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Top Expert 2014

UNC path means it using  SMB which is slow.

You may want to read:


Which gives you various ways to tune IIS, SMB, and other pieces of Windows 2008.


Thanks, pretty familiar with that doc though, there isn't anything the covers this particular issue there. General file transfers with SMB are fine (on the whole network), it's only with this instance of using a remote virtual directory in IIS that there's an issue.
Top Expert 2014

20MBps is not that bad when using SMB.  Unless you are using jumbo frames typically with Gbe the best you can get is 40MBps, assuming your disk drives can keep up with that, which most servers should have disks that can.

Since you are running Gbe you could try configuring for jumbo frames and see if that helps.


Like I said I'm not concerened with the speed on the LAN but the WAN speed decrease is an issue...
Top Expert 2014
This one is on us!
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James MurrellQA Product Specialist

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