Solved

diskpart command confusion

Posted on 2011-09-14
9
517 Views
Last Modified: 2012-06-21
I am following a process to create a pc to boot from vhd only.

http://blogs.technet.com/b/keithcombs/archive/2009/05/22/dual-boot-from-vhd-using-windows-7-and-windows-server-2008-r2.aspx 

Part of the diskpart command is to create a vdisk file.
Create vdisk file=c:\7ent.vhd maximum 40960 type=expandable.

I read this as the vhd file will max out at 40gb and the vhd should be large enough to install Window 7.

When all is complete and I do boot from the vhd and check the size of the VHD, it is already 40gb.

What am I missing? What is the point of setting a maximum and type =expandable if the vhd will already be 40gb.

I also tried creating a vhd file only 7gb (large enough to install windows)  If I try to copy above the 7gb I get the message not enough disk space. No being expanded.

Can someone explain this to me?

All help is appreciate.
0
Comment
Question by:maquet
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
  • 2
9 Comments
 
LVL 120
ID: 36537366
The VHD that is being booted from will expand to the maximum size specified at creation.  It will revert to the used size when you shut it down.  
0
 
LVL 5

Expert Comment

by:megaman5
ID: 36537372
When you boot the vhd?  I think it needs to tell the OS that the drive is 40gb for file system reasons.  I think the 'host file' (the vhd itself) will only take up an expandable amount of space on the host volume.  
0
 
LVL 120
ID: 36537384
In answer to your question, storage of the VHD, when the machine is off, it will use less disk space, but also a word of caution here, you must ensure, you have at least the expandable size, to start to boot the machine.

So this process will allow you to boot multiple machines (at different times), as the stored machines will be less.

Some people confuse this with VMware Thin provisioned disks. Where disks start small (due to storage in use) and grow to the max of the disk and stop.
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:maquet
ID: 36537399
So if boot from a usb stick and look at the size of the vhd it will not be 40 gb?  
0
 
LVL 5

Accepted Solution

by:
megaman5 earned 500 total points
ID: 36537404
Wrong, just as thin provisioned disks, the on-disk space used is equal to the data size and meta data.

https://blogs.technet.com/b/ranjanajain/archive/2010/03/23/virtual-hard-disk-vhd-architecture-explained.aspx

Thanks!
0
 
LVL 5

Expert Comment

by:megaman5
ID: 36537411
If you are storing the vhd on a usb disk, and you are not booted to it, it should only show used size plus meta data.  There is no 'expanding and contracting' on boot and shutdown, just a layer of abstraction where the on disk size is kept as small as the data.

Thanks!
0
 
LVL 5

Expert Comment

by:megaman5
ID: 36537453
If the vhd didnt 'fake' the os thinking that it is 40gb, you would always be out of free space and applications would fail when requesting disk space.  so when you are booted to the vhd, it 'lies' to the os saying that its already 40gb, and just resizes in the background.
0
 
LVL 120
ID: 36537488
when you boot will always be the expandable size.
0
 

Author Closing Comment

by:maquet
ID: 36816586
Nice article but I still cannot do what I am trying to do.
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When you start your Windows 10 PC and got an "Operating system not found" error or just saw  "Auto repair for startup" or a blinking cursor with black screen. A loop for Auto repair will start but fix nothing.  You will be panic as there are no back…
There are many software programs on offer that will claim to magically speed up your computer. The best advice I can give you is to avoid them like the plague, because they will often cause far more problems than they solve. Try some of these "do it…
This Micro Tutorial will teach you the basics of configuring your computer to improve its speed. It will also teach you how to disable programs that are running in the background simultaneously. This will be demonstrated using Windows 7 operating…
This Micro Tutorial will give you a basic overview of Windows Live Photo Gallery and show you various editing filters and touches to photos you can apply. This will be demonstrated using Windows Live Photo Gallery on Windows 7 operating system.

738 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question