Question about Virtual Machines

[Hedgemon]

To my understanding, a virtual machine (VM) allows a user to be able to dedicate space and memory from hardware to run emulated software/operating systems in an environment. 

What I don't understand is how do these servers persist. If the hardware that hosts the VM needs to reset, how is the VM saved. Does a program (or a service)  have to be running at all times to keep the VM alive?
I would love to learn more about VM and their advantages and how you would set up a network utilizing them. 

If you have any information to share, please help me learn more. (or correct me if I've misunderstood)

[Jimothy]

Depends on the type of vm. Traditional virtual machines like the ones you see in VirtualBox or windows Hyper-V use something called a Hypervisor, which is essentially the master program on the host machine that is used to organize and watch over all of the virtual machines. When you allocate space for a vm, you are creating space for its emulated HDD as well. Data will be written and read from the emulated HDD in the vm as if it were a physical device. In theory if the host machine keeps the hypervisor's data, the vm's data will remain intact. One of the main practical applications of this to to allow a single host to act as many separate computers as once. You can compute at scale with this since not everything will be tied to the single computer, but can be distributed across multiple emulated ones.

These days containers are more popular for applications at scale, since they are similar to vm's but require the bare minimum resources that your program requires, as opposed to a traditional vmthat installs an entire OS. This doc from Microsoft has a pretty good overview of the two main types of VMs and how they work.

[SPlink :)]

On 7/1/2021 at 10:40 PM, Jimothy said:

Depends on the type of vm. Traditional virtual machines like the ones you see in VirtualBox or windows Hyper-V use something called a Hypervisor, which is essentially the master program on the host machine that is used to organize and watch over all of the virtual machines. When you allocate space for a vm, you are creating space for its emulated HDD as well. Data will be written and read from the emulated HDD in the vm as if it were a physical device. In theory if the host machine keeps the hypervisor's data, the vm's data will remain intact. One of the main practical applications of this to to allow a single host to act as many separate computers as once. You can compute at scale with this since not everything will be tied to the single computer, but can be distributed across multiple emulated ones.

These days containers are more popular for applications at scale, since they are similar to vm's but require the bare minimum resources that your program requires, as opposed to a traditional vmthat installs an entire OS. This doc from Microsoft has a pretty good overview of the two main types of VMs and how they work.

 

Great explanation

Hyper-V (which comes with every windows server instance) walks you through every step of the process

Create the vm, mount an .iso of the OS you want to install, go through the process of setting up the OS, and it's there

You can remote into the VM like it was its own computer or server (using mstsc) and work on it that way

Or go to the hypervisor or remote into the hypervisor and go to it from there

At my work we have different servers set up for different functions (file server, dns/dhcp server, terminal server, etc), and they're all virtual - we actually only have 1 physical server and 5 virtual servers