iSCSI SAN slower than NAS?

I have been testing out the DSS live cd and have found the iSCSI preformance to be lower than that of the SMB NAS... How can this be? I have tried several diffrent configurations for the iSCSI dameon options but found the defaults provide the best preformance. I am running the software on a P4 Dual Core 2.8Ghz with 2GB of DDR2 and a Perc3 SCSI Raid controler with a Broadcomm 10/100 nic (running at 100mbit.) On a RAID 0 array i am seeing about 6MB/s with the iometer software doing 512k operations with a 50/50 split on random/seq. and read/write. Not terrible. But when running a file copy test of 3 iso files totaling 1.77GB the copy time averages out to 10:00 min. to the iSCSI target and somewhere around 7:00 for the SMB share. Someone please help me understand why I am seeing better preformance off the SMB than i am off of iSCSI.

Thanks

Since block size critically affects iSCSI throughput, use realistic sizes for the block data.
While this can improve performance with certain kinds of data (notably backups and video editing where block sizes of 32 to 64K or even more are often useful), Microsoft uses the default 4K block size carefully. There may be no particular performance gain in changing it. However, a series of tests with Iometer will tell you more precisely what those gains might be. In fact, the two main factors affecting iSCSI performance are host performance and block size. While block size affects performance on any iSCSI SANs they are particularly affected by the host resources. The reason is that iSCSI requires a lot of processing power to wrap and unwrap SCSI packets in TCP/IP shells. Even with host bus adapters (HBAs) with TCP/IP offload engines (TOE) to handle the bulk of the processing, host processor speed and the amount of available memory can limit the performance of the iSCSI SAN. Adding more memory or an upgraded processor to the host will often substantially improve SAN performance. Ideally, you want to match the block size to the size of the data in a typical read or write operation.
Also check the CPU and Memory usage of the DSS. Go to STATUS -> hardware -> Server statistics and hit the Apply button to view what is happening.
Please check out this thread as this is similar situation that you are having.
http://forum.open-e.com/showthread.php?t=335
never heard back from him after asking them to please test with a 1GB NIC.