This post explains why when adding a 4K LUN as an RDM to a VM doesn't work
When a 4K block sized LUN is added to a virtual machine on an ESXi 5.5 environment you get the below error when trying to boot the VM.
Either recreate the Volume/LUN to one that is 512, upgrade vCenter and your ESXi hosts to version 6 or higher. In our case we were trying to P2V the OS of a SQL server and then move over the direct attached LUN to the VM. We had to back out our change since we were still on ESXi 5.5.
As designed. VMWare doesn't support 4k LUNs until after ESXi 6.
SageLike Post ID: SL0017
ESXi 5.5 and earlier