Reinstalling 8.1 with UEFI boot. Avoiding duplicate firmware entries

[bphlpt]

If I understand what you are saying, the "restoring in a few seconds" applies to restoring an image inside the VM, correct?  That is different than taking an image of a "real" install using Acronis True Image, Macrium Reflect, etc, and then later restoring that image back to actual hardware, not a VM, correct? I just want to be sure we're comparing apples to apples.  I assume the restoring to metal will, of course, take much longer.

 

Cheers and Regards

[jaclaz]

Among the many "virtual disk" formats a VM can use there is a "snapshot" one (which actually is comprised of a "base" image + one or more "differencing" images, see:

https://www.vmware.com/support/ws55/doc/ws_preserve_using_sshot.html

https://www.vmware.com/support/ws55/doc/ws_preserve_sshot_linear.html

https://www.vmware.com/support/ws55/doc/ws_preserve_sshot_tree.html

and:

http://sanbarrow.com/vmdk-handbook.html

http://sanbarrow.com/vmdk-basics.html#snapshots

http://sanbarrow.com/vmdk-snapshots.html#translatebuttons

 

It is an exceptional good method/way to do experiments, like change settings or install/uninstall applications, etc. as what it is saved at each "snapshot" taken is just the "delta" when compared with a base image, but it is not like if you completely change the contents of the virtual disk attached it will take the same few seconds to take the snapshot and/or to restore to a previous one.

Since when doing this kind of experiments the changes compared against the start are usually very small, then the time to take the snapshot and/or to restore to it are also very small, but if you change lots of things, then it will take a proportional amount of time.

As well, if you create a tree with tens or hundreds of snapshots, things may start to become not-so-fast.

 

The key here is to understand how a snapshot (or Redo) image is only "valid" if attached to it's parent image, and it only records the changes happened inside the VM when compared to the parent image (which is "established once and later remains unmodified"). 

 

HTH.

 

jaclaz

[NoelC]

If I understand what you are saying, the "restoring in a few seconds" applies to restoring an image inside the VM, correct?  

 

I guess the answer is yes. 

 

I'm specifically describing restoring a snapshot as implemented by VMware.

 

This is essentially the functional equivalent of restoring a backup image, in that everything in the virtual machine is set back to the time the snapshot was made.  After snapshot restoral the VM begins executing exactly where it was, with the same things on disk, when the snapshot was made. 

 

In fact, the snapshot process is even better than a backup / restoral in that a running system can be snapshotted, and when restored it will continue executing right where it was before.

 

-Noel

Edited June 6, 2014 by NoelC

[Soukyuu]

The whole snapshots thing only applies to VMWare's product though, or is VirtualBox capable of it too? I see a snapshot feature in VB, but the files it creates seem to be only an image of RAM, which seems kinda useless.

[jaclaz]

Well, VirtualPC has also them (they are called "differencing VHD's" and/or "Undo Vhd's" they are two types slightly different):

http://technet.microsoft.com/en-us/library/cc720381(v=ws.10).aspx

http://technet.microsoft.com/en-us/library/cc720325(v=ws.10).aspx

 

Also Virtualbox has "differencing images":

http://www.virtualbox.org/manual/ch05.html#diffimages

 

 

jaclaz

[NoelC]

The whole snapshots thing only applies to VMWare's product though,

 

I have only practical hands-on experience with snapshots using VMware workstation.  But I heard that at least some of the other virtualization packages had a similar function (jaclaz has confirmed this, above).  I don't know how fast their implementations are, though.

 

What's surprising is how mature virtualization technology is.  It really works, and it provides serious value for a developer.  For many things you can entirely eliminate a test lab by doing testing in virtual machines.

 

-Noel