Chapter 3. Creating a Virtual Machine

Guest virtual machines should be deployed and configured based on their intended tasks. Some guest systems (for instance, guests running a database server) may require special performance considerations. Guests may require more assigned CPUs or memory based on their role and projected system load.

Some guest virtual machines may have a particularly high I/O requirement or may require further considerations or projections based on the type of I/O (for instance, typical disk block size access, or the amount of clients).

Some guest virtual machines may require higher priority access to storage or faster disk types, or may require exclusive access to areas of storage. The amount of storage used by guests should also be regularly monitored and taken into account when deploying and maintaining storage. Make sure to read all the considerations outlined in Red Hat Enterprise Linux 7 Virtualization Security Guide. It is also important to understand that your physical storage may limit your options in your virtual storage.

Depending upon your environment, some guest virtual machines could require faster network links than other guests. Bandwidth or latency are often factors when deploying and maintaining guests, especially as requirements or load changes.

SCSI requests can only be issued to guest virtual machines on virtio drives if the virtio drives are backed by whole disks, and the disk device parameter is set to lun in the domain XML file, as shown in the following example:

<devices>
  <emulator>/usr/libexec/qemu-kvm</emulator>
  <disk type='block' device='lun'>
                

<devices>
  <emulator>/usr/libexec/qemu-kvm</emulator>
  <disk type='block' device='lun'>