What build of V6 are you using ? the latest is build 5087.
What firmware are you using on the RAID card? (latest DSS supports the latest firmware)
Have any adjustments been made to the SCST parameters, at each target?
Are you using jumbo frames? Do you have hardware that supports jumbo frames?
Have you tried these tests without the bond, or less ports in the bond? As bonding doesnt always provide a performance boost.
Are you using write caching on the RAID?


The reason I mention these things, is they will all have an impact on performance. You should investigate making some adjustments in these areas.
Searching this forum, and the open-e knowledgebase, it can help.
http://kb.open-e.com/