Installation guide

KVM provides two emulated PCI IDE interfaces. An emulated IDE driver can be
used to attach any combination of up to four virtualized IDE hard disks or
virtualized IDE CD-ROM drives to each virtual machine. The emulated IDE driver
is also used for virtualized CD-ROM and DVD -ROM drives.
T h e emu lat ed f lo p p y d isk d rive d river
The emulated floppy disk drive driver is used for creating virtualized floppy drives.
4 .3.2. Para-virt ualiz ed devices
Para-virtualization provides a fast and efficient means of communication for guests to use devices
on the host machine. KVM provides para-virtualized devices to virtual machines using the Virtio API
as a layer between the hypervisor and guest.
Some para-virtualized devices decrease I/O latency and increase I/O throughput to near bare-metal
levels, while other para-virtualized devices add functionality to virtual machines that is not otherwise
available. It is recommended to use para-virtualized devices instead of emulated devices for virtual
machines running I/O intensive applications.
All virtio devices have two parts: the host device and the guest driver. Para-virtualized device drivers
allow the guest operating system access to physical devices on the host system.
The para-virtualized device drivers must be installed on the guest operating system. By default, the
para-virtualized device drivers are included in Red Hat Enterprise Linux 4.7 and newer, Red Hat
Enterprise Linux 5.4 and newer and Red Hat Enterprise Linux 6.0 and newer. The para-virtualized
device drivers must be manually installed on Windows guests.
Note
For more information on using the para-virtualized devices and drivers, refer to the Red Hat
Enterprise Linux 6 Virtualization Host Configuration and Guest Installation Guide.
T h e p ara- virt u aliz ed n et wo rk d evice ( virt io - n et )
The para-virtualized network device is a virtual network device that provides network
access to virtual machines with increased I/O performance and lower latency.
T h e p ara- virt u aliz ed b lo ck d evice ( virt io - b lk)
The para-virtualized block device is a high-performance virtual storage device with that
provides storage to virtual machines with increased I/O performance and lower latency. The
para-virtualized block device is supported by the hypervisor and is attached to the virtual
machine (except for floppy disk drives, which must be emulated).
T h e p ara- virt u aliz ed co n t ro ller d evice ( virt io - scsi)
The para-virtualized SCSI controller device is a new feature in Red Hat Enterprise Linux 6.4
that provides a more flexible and scalable alternative to virtio-blk. A virtio-scsi guest is
capable of inheriting the feature set of the target device, and can handle hundreds of
devices compared to virtio-blk, which can only handle 28 devices.
In Red Hat Enterprise Linux 6.4 and above, virtio-scsi is fully supported for the following
guest operating systems:
Red Hat Enterprise Linux 6.4 and above
⁠Chapt er 4 . Int roduct io n t o Red Hat virt ualizat ion product s
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