So far looks fine, next steps to determine what is slowing everything down may be:
- disable bonding and use single Ethernet controller
- test the system without s/w raid, check if raid has completed initialization, which is a huge load for a cpu
- make sure option WB (WriteBack caching) is enabled when assigning volume to iSCSI target, which will slightly speed up data writing

After testing few possibilities you should be able to find the weakest link.