Samba read speeds very slow through Explorer, but OK through Firefox

Question

I have a file server running Ubuntu 12.04 and Samba 3.6.3. A Samba share is mapped to a drive on a Windows 8 machine.

When copying a test file to a local drive (which is an SSD and not a bottleneck here), it is very slow when doing so through Explorer. It is similarly slow when downloading the file through Internet Explorer. When downloading through Firefox (by entering the file URI), however, it is more than 10x as fast, as the image below shows.

What's going on here? I know that Samba is not fast, but I thought that's generally the case when dealing with lots of small files, when its request logic is very inefficient. The test file was 826 MB.

Answer 1

Removing custom "socket options" line in smb.conf (the Samba configuration file) solved it for me.

It seems that it's best to leave that option blank nowadays, since it will calculate optimal values itself. Firefox seemed to be either using its own SMB protocol settings, or ignoring those set by the Samba server.