HYPER-V: Virtual Hard Disks

2012R2

If I have a VHDX file:

Can I change its size?

Can you share a VHDX file between two VM's?  IF so why would you do this?  Is it best practice to have one VM per VHDX?

Thank You.
howmad2Asked:
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rhandelsCommented:
Hey howmad,

I see you asking multiple questions regarding Hyper-v and virtualisation. To be honest answering these questions isn't as easy as you might think. VHDX files can indeed be extended and be have a larger size (up to 64TB, but how usefull is that).

Here's a good starters article but it might be a better idea to let us know what you are trying to do. If you are creating a server farms and would like to virtualize it then you need a different answer than creating VDI machines for example.

http://technet.microsoft.com/en-us/library/hh831446.aspx
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You can change the sizes of VHDX, you can create Fixed Size and Dynamic Size VHDX (they'll expand in size as you put data in them!).

It is best practice to have a single VHD/VHDX per VM.

You cannot shared VHDX between VMs. (not easily, there are methods this can be done, to create Clusters between VMs)
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howmad2Author Commented:
I purchased 2 servers recently; a file server and app server.

Before it was delivered, the customer now wants to virtualize using hyper-v.  They want 2 VM on one server and three on the other.  they are big boxes, so im not concerned about memory (64GB) or Processor (Dual 6 cores - total of 12) and 1TB hard drive space.  The Apps are not cpu intensive.

BACKGROUND
I have a physical DC on site.  Simple network. a few servers and a dozen workstations and remote uses accessing the servers via VPN.

I do not have a SAN (because this was not the intended configuration)

I'm trying learn about Hyper-v as fast as possible, because my deadline has not changed.

I have installed the HOST, Hyper-v role and the Hyper-v manager.  I created a few VMs.

QUESTIONS
If I make the VHDX file too small , can I change it later?  

Should I just over allocate the VHDX file?  It seems you can make each VHDX file as big as the available underlying partition....whats the downside of doing this.

Should I use one VHDX file per VM?

I have a BDR that can create VHD files if a restore is needed.  Can a VHD file be converted to a VHDX file?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
If I make the VHDX file too small , can I change it later?  

- yes, select and Edit the disk, via the VM disk settings.

Should I just over allocate the VHDX file?  It seems you can make each VHDX file as big as the available underlying partition....whats the downside of doing this.

Always start small and grow......so if you need a VM with a 40GB disk, create a 40GB disk, be careful you do not allocate ALL hosts storage to your VDHX.

Should I use one VHDX file per VM?

Yes, but if creating disks, in the VM, use disks, not OS partions, so if you need a C: and D:, create two disks, do not use OS Partitions, because disks are easier to grow than partitions.

I have a BDR that can create VHD files if a restore is needed.  Can a VHD file be converted to a VHDX file?

yes it can,
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Lee W, MVPTechnology and Business Process AdvisorCommented:
You need to think logically about the VMs and understand, the more VMs / VHDs (and VHDx) files in use on a particular logical drive, the greater the disk use time and this can potentially slow things down.  WHERE POSSIBLE, use SSDs, FAST disks (15K) and multiple sets of spindles - a different mirror for each VM or a different RAID 10/0+1 for each VM would be ideal.  Otherwise, think logically about what the systems are doing and how much disk use they might have and allocate accordingly.

Disk use aside, if you use Dynamic VHD/VHDx files, it can make them easier to move around HOWEVER, your change of fragmenting them goes up considerably. For this reason, if you have to run multiple VHDx files on a physical drive/drive set, I recommend partitioning - by giving each VHD its own partition, you ensure fragmentation for that VHD as it grows is kept to a minimum (fragmentation and multiple VHDs can KILL disk performance).

VHDx and VHDs can be created LARGER than the size of the physical disk you store them on if they are dynamic.  My VM C: drive VHDs use Dynamic VHD files set to a maximum of 127 GB.  Having the smaller files allows me to migrate to different servers, pull copies for test networks, and over-commit disk space, but you DO have to watch it and be wary of fragmentation.
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Lee W, MVPTechnology and Business Process AdvisorCommented:
So, just to be clear, my information was completely useless to you?
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