The Red Hat VirtIO SCSI Pass-Through Controller driver is a Windows driver that allows a Windows virtual machine (VM) running on a Red Hat-based hypervisor (like KVM, QEMU, or RHEVSCSI controller for storage, specifically when the virtual machine is using VirtIO drivers. VirtIO is a set of paravirtualized I/O drivers that provide efficient communication between the host (hypervisor) and the guest (VM) operating system, improving performance compared to emulated hardware.

The VirtIO SCSI controller is a virtualized SCSI controller for high-performance disk I/O in virtual machines. It allows the VM to communicate directly with SCSI devices (usually virtual disks) that are passed through from the host system, optimizing disk access and providing features like hotplug (dynamic addition/removal of virtual disks) and better scalability.