DSS v7 is already certified with VMware ESXi 5.1. As DSS v7 has passed all of VMWare test conditions and passed them all successfully. Same for DSS V6 with VMware ESXi 4.x .
Please update your current DSS V6 build to the latest build available now, and check the performance again, if you still face issues, please open a support ticket, ans support us with your system logs files, the patch file number that you already used, and the performance that you are facing now. Thank you.
We have the same problem here with DDS V6 und ESXi 5. Especially removing snapshots takes endless time. I don't think that the iSCSI handling differs with the DDS V7 version so this problem might still exist. Maybe somebody can give information's about the iSCSI parameters of Open-E and ESXi 5 used as best practice in this environment.