iSCSI target is OpenSolaris 2009.6 (COMSTAR)
iSCSI traffic is in the separate VLAN, the target and all initiators use 9k jumbo frames, jumbo are enabled on switch.
iSCSI initiator on RHEL5 shows nice performance around 80mb/sec read, 80mb/sec write (copying the regular files/using dd, then doing sync, then calculating actual speed)
The problem is with the iSCSI initiator on Windows XP - very slow, can't get more than 20-25mb/sec. Network card: Intel 82574L, TCP offload is on.