[Samba] ridiculous slow gigabit transfer, faster with VNC

[Andrew Morgan]

On Thu, 19 Jul 2007, Mark Baily wrote:

> Hi,
> I have a problem with file transfers between a windows systems and unix 
> systems.
> I have one win32 desktop (intel e6400 2Gb Ram), one win32 laptop (p-m 2Ghz).
> Also one linux laptop (p-m 1.4GHz) and one opensolaris desktop (intel
> e4400 1GB Ram).
>
> The two laptops have built-in 100Mbit ethernet and desktops have 1Gbit
> ethernet on the motherboard. Both desktops use a Marvell Yukon.
>
> The file transfer rate between two systems using FTP between the two
> desktops (win32 to opensolaris) is consistently 50Mb/sec which is as
> expected.
>
> Using scp I only get 5Mb/sec between from any win32 system to any unix
> system, much slower than expected.
>
> Using scp from the linux lapotp to solaris desktop is 10Mb/sec as
> expected (laptop has 100mbit only).
>
> Using samba to copy a 1GB file I get about 7 minutes from win32 to
> opensolaris. From opensolaris to win32 the windows dialog says
> estiamted time 142 mins. Using plain FTP it takes 25sec. This is very
> consistent.
>
> A twist is that if a VNC client is open from the win32 desktop to the
> opensolaris box the estimated transfer time via samba from opensolaris
> to win32 drops right down to about 4 min. Much better, but still
> nowhere near the FTP.
>
> I have also tried swapping between a D-Link DGS-1008D switch and a
> Netgear GS105 switch with no difference.
>
> Since the FTP is very consistently acheiving 50megabytes/sec, I don't
> think it can be blamed on a hardware fault.
>
> However the problem doesn't appear to be just samba either, as the
> slowness also occurs with scp, albiet scp is much more consistent at
> 5mb/sec than samba varying at 1GB/142min to 1GB/3min with VNC open.
>
> Is this problem something to do with TCP stacks playing up? What else
> might it be?

Have you confirmed that you do not have a duplex mismatch?  I don't know 
if D-Link or Netgear (consumer grade?) switches can be queried for the 
duplex setting or forced to full duplex.  Usually this stuff "just works", 
but the behavior you describe sounds very much like the switch is half 
duplex and the server is full duplex.

 	Andy