The Lite version has some limitation, as it does not support 10 Gb Ethernet, or Multiple CPU Support, etc.. for more details about different between Free Lite version of DSS and the full DSSv6, please visit this link: http://www.open-e.com/products/open-e-dss/comparison/

Also you said you have 8x600GB HDD, that means you have 4800GB (4.8TB) ? as the Lite is only designed to deal with 2TB of storage. while the Full DSS can deal with unlimited size.
So please try with the full DSS version, also try to tune your system, to match the same as other products, and please try to test both, as all can claim, right!