Questions about virtual machines

[Arkitech]

I've been thinking of installing a VM on my vista machine so I can make a backup image in the event of a virus or crash. I'm assuming that VMs will need to use the host machines devices and drivers so it seems like a good idea for making backup images.

I was also wondering if a VM session was infected with a virus would it spread to the host machine?

Is it possible to run servers from within VMs?

Is it practical or would it be too taxing on the host machine? I've been wanting to install Exhange and Server 2008, I was thinking VMs might be the way to go.

 

[Czar]

backup image?


but anyway, the vm behaves just like a normal machine, has its own virtual hardware and even bios. Your host machine will get a little bit slower because running a vm is just like running a heavy application. It needs cpu, memory and disk access.

For the most part you will need alot of memory. If your host machine has 2gb memory and you create a vm with 1gb memory you will only have 1gb left for the host. When you boot the vm it will have alot of disk IO, which means lots of slowdowns for the host.

You can get around alot of that by giving the host alot of memory and using dedicated disks for the vm's.

If you want to go further and have a spare machine with specified hardware you could run the free vmware ESXi server. That means your OS is ESXi, you connect to it through a browser, and there you can create vm's.

Whats great about ESXi is that it has memory sharing. Which means that if you create a windows vm with 1gb memory, you boot it up and it will only take about 300mb, the rest is not used so its not reserved for the host. When you create the second windows vm it gets even better because two windows machines have alot of the same dll's loaded but ESXi only puts it once in memory. So the first vm takes maybe 300mb, the second vm will maybe take just 200mb. Then on a hardware host with 1gb memory you can have vm's that have more than 1gb in memory.

And yes, its very possible to run servers as vm's, I run about 60+ virtual servers at work on 6 hosts, we even could run all those vm's on 3 hosts. Companies that do not run vm's are very very rare today.

Next stop, desktop virtualization

 

[Arkitech]

Originally posted by: Czar
backup image?


but anyway, the vm behaves just like a normal machine, has its own virtual hardware and even bios. Your host machine will get a little bit slower because running a vm is just like running a heavy application. It needs cpu, memory and disk access.

For the most part you will need alot of memory. If your host machine has 2gb memory and you create a vm with 1gb memory you will only have 1gb left for the host. When you boot the vm it will have alot of disk IO, which means lots of slowdowns for the host.

You can get around alot of that by giving the host alot of memory and using dedicated disks for the vm's.

If you want to go further and have a spare machine with specified hardware you could run the free vmware ESXi server. That means your OS is ESXi, you connect to it through a browser, and there you can create vm's.

Whats great about ESXi is that it has memory sharing. Which means that if you create a windows vm with 1gb memory, you boot it up and it will only take about 300mb, the rest is not used so its not reserved for the host. When you create the second windows vm it gets even better because two windows machines have alot of the same dll's loaded but ESXi only puts it once in memory. So the first vm takes maybe 300mb, the second vm will maybe take just 200mb. Then on a hardware host with 1gb memory you can have vm's that have more than 1gb in memory.

And yes, its very possible to run servers as vm's, I run about 60+ virtual servers at work on 6 hosts, we even could run all those vm's on 3 hosts. Companies that do not run vm's are very very rare today.

Next stop, desktop virtualization

Wow, thanks for all the info. This is really eye opening, I had no idea that VMs were used that way within companies now days.

So what kind of host hardware are you using? Also what VM software do you guys use at the job? Is it the ESXi or something else?

 

[Czar]

Your welcome

And another thing, at work every new machine that is needed is defaulted as a VM unless there is some specific need for hardware. The need is mostly just dongles or if there is some specific special hardware that needs to be connected, sometimes also if the software vendor does not support their software running on a vm, but thats only when its software we dont know.

We are using IBM blades with AMD processors, most with 16gb of memory, a few with 12gb I think. And we are using ESX and not ESXi, the difference is with ESX you have a small vm running there that runs a modified version of Red Hat so you have direct access to the hypervisor. That console vm is different from other normal vm's because it can touch the hardware, other vm's have no access to the hardware.

But when we upgrade to Vsphere4 which is the newest version we will probably use ESXi because we are betting that VMware will drop ESX in the next version and only offer ESXi. Simpler basicly.

And two neat features that make virtualization awesome you can move a running machine frome one host to another (vmotion) without any downtime and you can move the vm file itself from one datastore to another (storagemotion) without any downtime. VMware has had vmotion for I think about 5 years, Microsoft with their Hyper-V software just managed that this year. Storagemotion became available from VMware 1-2 years ago when version 3.5 was released. Microsoft sooo behind its kinda sad really

The other big vendor in the field along with VMware is Citrix with their Xen platform.

 

[0roo0roo]

lol yea vms use a generic virtual machine. they do not clone your hardware into a matrix version

you want to make a backup image of your os, use driveimage xml, it will do it from within windows...no reboot necessary.

with enough hardware you can run network access programs within vm's. virtualbox is free for you to fiddle with. and yes you can backup the image of the vm. but you can't backup your main os from the vm. its separate.