Samba on Debian Lenny much slower than Windows 2008

I have a VMWare ESXi 4 server running two virtual machines. The host server is a quad core AMD Phenom II with 8 GB RAM and a RAID-5 SATA-II array.

The Debian VM is Debian Lenny with latest updates - x64 version base system install only with samba installed on top (i.e. there's no GUI, it's very lean). Filesystem is XFS.

The Windows VM is Windows 2008 x86 Enterprise Edition with all latest updates.

I have configured both VMs to use 1 vCPU and allowed them to have 2 GB RAM. I copied a 3 GB file multiple times to each one and recorded the times.

• Lenny: 2mins 35 avg
• Windows: 45 secs avg

Does anyone have any tips to get the Debian system to match the same speed as the Windows one? Windows is 3.5x faster. They are both using the same hardware, so it's puzzling that the Debian machine is so slow - I think it might be samba, but I'm not sure.

Thanks, Mark.

UPDATE: The client OS is Windows 7

UPDATE2: I just tried the same test on a Windows 2003 VM with the same resources allocated and the average time for that was 49 secs, slightly slower than Win2008 but Debian Lenny is still much slower.

Have a read of the Debian section of the VMware - Guest Operating System Installation Guide and make sure that the VMware Tools are installed and note the following:

• When running a 64‐bit Linux guest operating system on EM64T hardware, make sure that you have Execute
  Disable functionality enabled in the host BIOS. This helps to ensure that the Linux guest operating system runs without interruption.
• With many Linux guest operating systems, various problems have been observed when the BusLogic virtual SCSI adapter is used with VMware virtual machines. VMware recommends that you use the LSI Logic virtual SCSI adapter with this guest operating system.

Also check the Vmware Guest Compatabilty Guide for any Debian specific requirements including recommendations on virtual hardware types to use.