So your are using the iSCSI Target on the DSS V6 then connect the XEN to the DSS Target and you are not able to install a virtual machine? What about creating another target with Block IO and try with another OS like MS?
The open source version Xen may only run 32bit DSS in your VM, so try that as well.
Also, typical opensource VM's can, on occasion, emulate hardware improperly, and instead load generic drivers for things like NICs. Make sure you have the support you need for this, in CentOS.
And as To-M said, how much RAM ? .... I would go for at least 2GB as well, if not 4GB.
i increased to 4G ram and used 32bit but without luck. i am unable to enter anything to select 32 bit or 64bit. it shows up the startup screen but no response to any input.