Dynamic disks and VMWare

Essendon

I know that if you convert a disk (that has multiple OS's) to dymanic only one operating system will run. But what if I have a virtual machine i.e. a virtual 2003 server, on the disk and convert the disk to dymanic? Will the virtual machine still be usable??

What got me thinking was that since the virtual machine running on the free VMWare server was not part of the bootup (or a boot OS), it would be ok to go ahead and convert my disk to dynamic. Thought it would be better to ask than to take the plunge and find the virtual machine not working...

If it helps in giving me an answer: The system files are on C, and the VMWare server and virtual machine are on D. Thanks!

astorrs

Just to clarify, you want to change the Host O/S's disks to virtual?

Essendon

astorrs wrote:

Just to clarify, you want to change the Host O/S's disks to virtual?

No, from basic to dynamic.

astorrs

Sorry that's what I meant.

Host O/S disks to dynamic?

Essendon

astorrs wrote:

Sorry that's what I meant.

Host O/S disks to dynamic?

Yeah.

astorrs

Ah then go ahead, the guest won't notice anything. I'll explain why in a sec.

Essendon

Oh ok then, I am going to do it now. I'll wait for your detailed answer though.

astorrs

VMware Server/Workstation and Microsoft Virtual Server/Virtual PC are host based server virtualization products, in that they require a host O/S (either Windows for both - or Linux in the case of VMware) to handle the actual communication with the underlying hardware.

Think of it in layers (I'll talk about Windows and VMware Server here).

1. At the bottom we have the physical hardware, CPU, RAM, storage, network 2. Above that is the Host O/S whose HAL and applicable drivers controls all communications with the layer below it 3. Above that is the virtualization software which (among other things - memory management, resource scheduling, etc) provides a set of standard virtual hardware (motherboard, video card, NIC, etc) to the guest virtual machines. It does not provide a standardized "virtual" CPU and instead allows the guest to see the actual type of CPU in the physical machine (if it had to interpret the commands for a virtual Intel CPU on a machine with physical AMD CPU's there would be translation involved and the speed would be horrible - Virtual PC for the Mac of previous years for example) 4. Above that is the virtual machine. As far as it is concerned it is the only machine there is. It doesn't know its "virtual" It sees all the "standardized virtual hardware" as physical components. As you've no doubt seen it even has a BIOS. 5. Above that is the virtual machines O/S which again has no idea its running in a virtual machine

Any given layer can only see down one level. Therefore a change made to storage at the Host O/S level is invisible to a guest virtual machine (it still sees the same hard disks - which are just files - and virtualized storage adapters, etc).

VMware ESX, Citrix XenServer, Microsoft HyperV, Virtual Iron, etc are hypervisors that do not require a host O/S. They essentially replace layers 2 & 3 and as such provide better performance, stability, etc.

Keep in mind that this is a greatly simplified overview of what is happening both at the hypervisor level and in the Windows host O/S (read Windows Internals if you want to really understand how things work there), but it's late here and I want to go to bed so I hope it'll do.

Essendon

Hey, that was bloody well explained Andrew! After reading this, I noticed the VCP in your ever increasing list of certs. No wonder, you have your concepts very clear. I changed the disk to dynamic and the computer rebooted a couple of time to finalise the conversion and it's good to go now. Thank you!

JDMurray

As a side note, TechExams does have an entire forum dedicated to the discussion of virtualization topics.

whistler

MobilOne wrote:

I know that if you convert a disk (that has multiple OS's) to dymanic only one operating system will run. But what if I have a virtual machine i.e. a virtual 2003 server, on the disk and convert the disk to dymanic? Will the virtual machine still be usable??

What got me thinking was that since the virtual machine running on the free VMWare server was not part of the bootup (or a boot OS), it would be ok to go ahead and convert my disk to dynamic. Thought it would be better to ask than to take the plunge and find the virtual machine not working...

If it helps in giving me an answer: The system files are on C, and the VMWare server and virtual machine are on D. Thanks!

Put bluntly Dynamic disk is crap! Unless you reallllly need to do software RAID don't use dynamic disks.

Your initial question. The virtualized servers won't care if the disk is basic or dynamic as astorrs so aptly explained.

Which is why MS can offer from download a virtualized demo Exchange 2007 server.
http://www.microsoft.com/downloads/details.aspx?FamilyID=692a6e3c-81c9-4d8a-93fa-266d651735dc&displaylang=en

With no mjor hardware requirements, other than disk space and memory.

dynamik

I've had to extend volumes before, so sometimes they're a necessary evil. I have HW raid underneath though, so I'm not going to lose everything if a drive dies.

astorrs

dynamik wrote:

I've had to extend volumes before, so sometimes they're a necessary evil. I have HW raid underneath though, so I'm not going to lose everything if a drive dies.

Extending the partition/volume onto the same disk or another disk?

If its unallocated space on the same basic disk, just use diskpart.

- Open a command prompt, run "diskpart"
- Enter "list volume" to display the existing volumes
- Enter "select volume <vol#>" where the volume # is the one you want to extend
- Enter "extend" (you can also specify the size with "size=")
- Enter "exit" to quit diskpart.

I'm also not a fan of dynamic disks, it makes troubleshooting disk failures or performing low level recovery with 3rd party tools far more difficult than it need be.

dynamik

Another set of drives