Let’s say you want to extend existing disk on your already installed VM. Usually to extend the existing ext4 partition where system is running you would use some Live CD, to edit partition while it’s unmounted. However it’s possible to extend the partition without booting from Live CD. Here are some simple steps to do so:
The concept is pretty simple. It’s like the top program, but instead of CPU and memory usage, it monitors disk I/O. If you have a system that is extremely slow to respond, but can’t seem to figure out what is going on, give iotop a try. You’ll probably have to install it, as I’ve never found a system with iotop installed by default, but it should be in the software repository of just about every Linux distro.
KVM (Kernel-based Virtual Machine) is, on the other hand a full virtualization solution for Linux containing virtualization extensions (Intel VT or AMD-V). Using KVM, one can have Linux and Windows virtual machines running side by side on the same hardware. Each virtual machine has private virtualized hardware: own kernel, a network card, disk, graphics adapter, etc. Since it has its own virtualized hardware, the virtual server will act completely on its own.