I have two production servers that I would like to upgrade from 4.1.0 GA 260247 to 6.0 U1. One is a Dell PE R910 and the other a PE R710, both of which are on the HCL for 6.0. I'm running the Essentials version, have Vcenter installed on a standalone computer, but haven't really done much in VCenter. As of the 4.1 version VCenter seemed overly complex for what I was using VmWare for. It was easier to perform day to day tasks just using the VSphere client. Over the years, after reading so many articles about problems with ESXI upgrades failing, I decided to forego the updates unless there was a business reason to do so. Version 4.1.0 GA of ESXI has been rock solid for me and runs for months on end without a reboot.
Now I need to upgrade some servers to Windows Server 2012 R2. Although I can get by with 5.x, it seems silly to spend the labor time, when I can future-proof to a degree with 6.x and end up with a speed-improved web client. I'm also hoping that USB 3.0 support for portable hard drives will finally be available and reliable as I use a physical server for guest OS and data backup employing portable drives instead of tape.
I know I need to perform the upgrade in two stages, 4.1 to 5.x, I assume 5.5 U2, then 5.x to 6.o U1. I'm not concerned with upgrading VCenter as there isn't much in that database due to my not using it. A fresh install of VCenter would be in order. For obvious reasons, I haven't found a definitive guide to upgrading 4.x to 6.x. I don't use a SAN, any optional features or plug-ins. All drives are local. I'm not sharing any datastores between guests. Both host servers boot from built-in SD card sockets. Could you point me in the right direction to accomplishing this task?