Installation guide

virtio-scsi is the recommended para-virtualized storage device for guests using large
numbers of disks, or advanced storage features such as TRIM.
virt io - b lk
virtio-blk is a para-virtualized storage device suitable for exposing image files to guests.
virtio-blk can provide the best disk I/O performance for virtual machines, but has fewer
features than virtio-scsi.
IDE
IDE is recommended for legacy guests that do not support virtio drivers. IDE performance is
lower than virtio-scsi or virtio-blk, but it is widely compatible with different systems.
CD - RO M
ATAPI CD-ROMs and virtio-scsi CD-ROMs are available for presenting ISO files or the host
CD-ROM drive to guests. virtio-scsi CD-ROMs can be used with guests that have the virtio-
scsi driver installed. ATAPI CD-ROMs offer wider compatibility but lower performance.
USB mass st o rag e d evices an d f lo p p y disks
USB mass storage devices and floppy disks are available when removable media is
required. USB mass storage devices are preferable to floppy disks due to their larger
capacity.
4 .5.4 . Host st orage
Disk images can be stored on a range of local and remote storage technologies connected to the
host.
Imag e f iles
Image files are stored on a host file system. The image files can be stored on a local file
system, such as ext4 or xfs, or a network file system, such as NFS.
Tools such as lib g u est f s can manage, back up, and monitor files. Disk image formats on
KVM include:
raw
Raw image files contain the contents of the disk with no additional metadata.
Raw files can either be pre-allocated or sparse, if the host file system allows it.
Sparse files allocate host disk space on demand, and are therefore a form of thin
provisioning. Pre-allocated files are fully provisioned but have higher
performance than sparse files.
Raw files are desirable when disk I/O performance is critical and transferring the
image file over a network is rarely necessary.
q co w2
qcow2 image files offer a number of advanced disk image features including
backing files, snapshots, compression, and encryption. They can be used to
instantiate virtual machines from template images.
qcow2 files are typically more efficient to transfer over a network, because only
sectors written by the virtual machine are allocated in the image.
LVM vo lu mes
⁠Chapt er 4 . Int roduct io n t o Red Hat virt ualizat ion product s
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