Simple files can be used as virtual block devices containing Xen domains. This is the quickest way to get started using Xen. We used them in Chapter 3when we were setting up various operating systems to run as Xen guest domains. In Chapter 3 in the Time for Action—Bootstrapping an Ubuntu system we created the files that hold are guest domain and then installed Ubuntu on them.
We created the files for holding the guest domain and then installed Ubuntu to them in Chapter 3.
File-backed virtual block devices are a convenient way to get started with Xen. We use the venerable dd
command to create the file that will be used to store our image. Doing this ensures that the file will be sparse, and space will be allocated only as parts of the file are used, not up front when the file is created.
Although files are a simple and quick way of storing VMs, there are some disadvantages of using files as virtual block devices:
They are not suitable for I/O-intensive uses, as they experience some...