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I am considering running HyperV for all my servers, because backup and disaster recovery plans are easier, when I can move the images around to any hardware and not have to worry about drivers.

However, my machines are not powerful enough to house maybe more than 1 or 2 virtual machines.

Does running 1 virtual machine on a box make sense?

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10 Answers

up vote 6 down vote accepted

We do this with one of our demo environments for the sole reason that it can easily be backed up, blown away or moved to a developer's machine for tweaking.

The reason why we only run one is due to the high system requirements of the demo (CPU usage and memory usage). Having multiple running at the same time is not feasible.

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While Jim is correct about the additional administrative overhead, virtualizing the server now will allow you to easily move it to a different server a week, a month, or a year from now when you have newer/better/faster hardware to run the virtual machine. You didn't mention the workload (I/O intensive applications like SQL server would not be the best candidates), and the decision is certainly about making tradeoffs, but if your priorities are around disaster recovery and server mobility, I'd say go for it.

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How is that easier? Back up server, load Hyper-V, create VM, recreate server on the Guest OS. OR... In the future get some real hardware. Load Hyper-V, and do a P2V migration. Done. –  Jim March Jun 5 '09 at 16:54
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I'm not sure how much you value your time but moving a VM file to another piece of host hardware is infinitely easier than trying to do a bare metal recovery of a tape backup using a backup agent. –  Kevin Kuphal Jun 5 '09 at 18:25
    
Related, we virtualize everything in our 300 person environment from SQL to Exchange and have no issues with I/O, resource utilization, etc and we're on a 12:1 VM to Host ratio in ESX 3.5 on 2 hosts. –  Kevin Kuphal Jun 5 '09 at 18:28
    
"12:1 VM to Host ratio" That is fine and dandy. Has nothing to do with someone wanting go with a 1:1 ratio though. Not mention he wants to do it on Hyper-V, which means he'll have to patch both the Parent and Guest OS every month. And I'm not sure how many bare metal restores you've had to do, I've done 1 in 15 years with EDS/HP. If your hardware is redundant, you should be good. If the OS is corrupt, virtualization doesn't help you. –  Jim March Jun 5 '09 at 19:46
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If you're getting your feet wet with virtualization, I'd say it's definitely worth it for the learning process alone. You gain a degree of hardware independence - isolated hardware failure involves minimal downtime of any critical system before it's spun up on a different host.

Nobody's even mentioned how fearless you can be about installing patches and version upgrades to VMs, since catastrophic problems are erased with a snapshot. This saves me a lot of time, and has allowed us to make some improvements we couldn't afford in risk/downtime previously.

The ease of future consolidation has already been brought up. I think overall, it's a step forward.

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Its not a bad idea, but I would try it out first to see how your performance it. It will make it real easy to move machines in the future when you do upgrade. You are not doubling the OS since the Hyper-V part of it is designed to not consume resources it doesn't need but you would have to ensure its properly take care of.

I would take a look at ESXi from VMWare. its a 32meg hyper visor, scaled down on features but is designed for a production setup.

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For all of your systems I would not think that makes sense, though the type of systems you plan to put in place would matter.

To run one one virtual machine on one box has only one benefit, the ability to restore it somewhat quickly if it crashes. But you really are wasting resources the could be better utilized toward server services.

You say the that the backup is easier, but is it? You still need to backup your host machine. I mean you don't want to have to reload it from scratch, then load all the patches before you can get your VM up and running? What are you saving there?

Invest in a true backup software application like Backup Exec with it's Disaster Recovery add-on, this will allow you to reload servers straight from tape if they need to be rebuilt.

If you are running 2 VM's on a machine, maybe it's worth it, but probably not. You are still better running the services right on the host OS.

Perhaps I (we) could give you a more direct answer is you could give some details on the environment you are thinking about visualizing.

One point I thought of, is that recovery could be moved to a machine already setup up a Hyper-V host, very quickly

Brett

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On my VMware clusters, I barely need to back up my host machines. I can build a new ESX server on basically any hardware in a matter of minutes from scratch and have it ready to launch Virtual Machines. Having servers as Virtual Machines means I can run them on anything very quickly (from desktops running VMware server to servers from any hardware manufacturer). –  Kevin Kuphal Jun 5 '09 at 18:27
    
"On my VMware clusters, I barely need to back up my host machines." Right.... And Macs don't need Anti-Virus. –  Jim March Jun 5 '09 at 19:42
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There are many other advantages as well as disadvantages to virtualization. You didn't mention your workload on your servers so you'll want to do some testing to make sure it will work for your environment and workloads. You may find that for the more I/O intensive servers virtualization may have too much overhead. Otherwise I think that you'll find that virtualizing the servers will work out better for you in the long run for the following reasons.

  • At the moment you may not have machines powerful enough to run multiple guests that will change in time and consolidating on newer hardware will be very easy to do. So planning ahead now will save your company time and money down the road.
  • It sounds like you have multiple physical servers but you didn't mention it but if your guest OS images will be on a shared storage (NAS or SAN). If so you will be able to live migrate your virtual servers between the hardware for maintenance.

There are of course many other advantages to virtualization.

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you need to bear in mind that to get a good backup, the guest needs to have its internal memory state saved to disk. Its no use backing up a running VM!. Suspending a VM requires some downtime, so if you need 24x7 uptime, this is not the best solution for you - you will end up making backups using backup software running inside the VM, and if you're doing that, you might as well run the VM on bare metal instead for the better IO.

If you shell out for expensive backup software, you can run your 1 machine on the bare machine, and your backups will still be good. You can run simple backup software like Acronis or R1soft's CDP on your machine and it will happily save the entire system state continually throughout the day, giving you much more up-to-date backups. Restoring may be more difficult than simply copying a VM image back, but if you've lost your host OS too then you're in no better position in using a VM at that point anyway!

VM guests do have some advantages to fancy backup software, you can store several versions, you can rollout upgrades and patches immediately after a backup so you can restore quicker if it proves to not work (and even easier if you use snapshots).

I think, all in all, if your VMs are so resource-hungry that you can only run 1, you might as well invest in the appropriate backup software and use that instead. The problem is that you will need much better hosts to run the image as virtualisation typically gives you less CPU and memory, but also significantly less disk and network IO.

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Not on VMware ESXi. You can snapshot a running VM with no downtime in order to back up the underlying Virtual DIsk. –  Kevin Kuphal Jun 5 '09 at 18:29
    
That is incorrect. A snapshot allows you to preserve the state of the virtual machine, but it is entirely dependent on the original VMDK in order to be of any use as a backup. Just backing up snapshots is not a backup up your VMs. –  Jim March Jun 5 '09 at 19:40
    
yes, I know VMWare can do it - but the question was about Hyper-V. Snapshots - you take the snapshot, suspend, and make a backup from it. The snapshot simply means you get a more incremental backup as the original files will not have been changed. Snapshots also help rolling back changes to a live system without needing to backup. –  gbjbaanb Jun 21 '09 at 15:37
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I think you should be fine, like has been said - it will be easier to move your machine once virtualized if you want to move to different hardware in the future, In the case of Hyper-V, providing that the services running on the box support vss writers you can backup a running VM using windows server backup (once you register the vss writer for Hyper-V) without any downtime, we do this nightly on a box running server 2008 x64 standard.

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If the parent OS is any competent, it would hardly need any reboots, locking down, patching etc, etc.

I think the purpose of VMing applications is to abstract the software from the hardware, this allows me to migrate/clone/snapshot whatever OS and applications without thinking too much about the hardware itself.

But of course if the hardware is any competent it would be able to support more than 1 VM per physical boxs. If the VM product is any decent it would allow me to at least cold-migrate/clone. If the VM product is enterprise ready it would at least allow me to live-migrate/manage load on vm clusters.

Backup should be the last of my worries since setting up a self-suffice vm infrastructure is already a daunting task, backups easy as cake.

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You would be essentially doubleing the number Operating Systems you need to support, since Hyper-V IS another OS that would need to be managed, patched, locked down, etc...

Not to mention the wasted resources on the Parent Partition.

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Wow, I can't believe someone down-voted, suggesting that taking say a 300 Physical boxes and making it 600 Operating Systems is a "Good Solution". This is just as bad as people that go from 300 Physical boxes, to 100 Physical boxes, but then start creating VM's like wildfire creating over 600 Operating Systems to manage. People really need to understand the purpose of virtualization before just jumping in! –  Jim March Jun 5 '09 at 19:38
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