Figure 3.24 displays the standard SCSI controllers that ESXi makes available to the guest OS.
Figure 3.24. Standard SCSI controller options.
Among the available options, BusLogic offers a greater compatibility with older-generation operating systems. LSI Logic Parallel offers a higher performance on some operating systems, but a driver must be added.
The VM VMware Paravirtual device driver is used mainly for heavy workloads. It directly accesses the virtualization layer. This driver is said to be paravirtualized because it interprets requests from the guest OS and sends them directly to the hypervisor. This reduces request interceptions by the Virtual Machine Monitor (VMM), which improves performance. This option works only with Windows Server 2003, Windows Server 2008, and RHEl 5.
Another available controller, VMDirectPath I/O, is a storage I/O driver that allows direct access to the physical device without going through ESXi’s virtualization layer to benefit from all the driver’s native functionality and performance within the VM.