Are you using the Dell ESXi installation? [URL] 
Hello, I have a server Dell PowerEdge T620 and I want to install VMW VSphere Hypervisor 5.5 on it. I tried 2 ways above but they are not success. Way 1:- Boot with DVD integrated with server- Config to RAID 5- Choose "VMW ESXI 5.5 HDD" option- Error: "provided raid configuration is not supported" and force me reboot. Way 2:- Boot using ESXI 5.5 CD- Follow step on install screen.- At the step scan HDD to install the process is scan too long too long.... I hope some idea can help me resolve that. Thanks !
Can not install ESXi 5.5 on Dell PowerEdge T620