Today while transferring ~1gb data base extract file between the test and 
production Oracle servers for TPC (Sun) on the same switch we were getting 
horrible transfer rates even for ftp (which I temporarily re-enabled ). It 
turns out (thanks to Robb J. for the heads) - the Suns were setting 
themselves by default in half-duplex mode.

# dmesg | grep Duplex
Jul 29 19:36:50 wsdb02 hme: [ID 517527 kern.info] SUNW,hme0 :   100 Mbps Half-Duplex Link Up

Use these settings in /etc/system to force the NIC into 100MBS:

# Force adapter into 100MPS Full-Duplex
set hme:hme_adv_autoneg_cap=0           
set hme:hme_adv_100T4_cap=0
set hme:hme_adv_100fdx_cap=1
set hme:hme_adv_100hdx_cap=0
set hme:hme_adv_10fdx_cap=0
set hme:hme_adv_10hdx_cap=0
set hme:hme_adv_100T4_cap=0
# End force FDX