Create and Use Hyper-V Checkpoints in Windows 10  

GalaxyGe said:

Are these checkpoints independent from each other? Or do they store the system state in differencing images? If so, how would we merge them?

To keep or restore a vm from a backup, would it be sufficient to backup that one relevant checkpoint and the relevant configuration file only?

To store a backup, does it matter if the vm is in SAVED or OFF state?

thanks in advance
Gerhard

Interesting question. Are each checkpoint relative to last one (like incremental backups in Macrium Reflect), or is each only relative to initial start point (like Macrium Reflect differentials).

If you can delete intermediate ones, they are more like differential backps. If not, I guess they are more like incremental backups.

Edit: just did a simple test

1) created an initial checkpoint 1

2) copied a desktop icon (so two of them), and created checkpoint 2

3) did same again so three icons, and checkpoint 3

4) Finally, same again - four icons, checkpoint 4

I could move up and down checkpoint chain reverting to status of chose checkpoint

Then I deleted checkpoint 2, and it did a merge process (merging info in checkpoint 2 with info in checkpoint 3 as far as I can tell).

I ran up and down chain reverting to checkpoints 1, 3 and 4.

So, as far as I can tell, the checkpoints behave in part like a incremental backups ie info in checkpoints are linked ie. each checkpoint is relative to previous.

However, if you delete one, its info is merged with next one. Macrium incrementals have a similarish merging facility (incrementals forever).

So I would say overall they work more like incremental backups, rather than differential backups, but also in a way partly behave like differential backups where if intermediate ones are deleted, later ones are not affected (this is a consequence of merging info in next one as one gets deleted).

This is quite impressive.

Edit 2 - after a bit more testing, I have realised when you delete a checkpoint, its info is merged with the now state, not with next checkpoint. This is more analagous with the sytnthetic full backups of Macrium Reflect.

In the end outwardly, they work like differentials, as you can delete intermediate ones, but are linked like incrementals. So they have a sort of hybrid behaviour.

This is all intellectually all a moot point though - in the end, click on a checkpoint, and vm reverts to that status.

This is fully reversible. Delete any checkpoint and that point is gone forever - you can only go to an earlier or later point.

GalaxyGe said:

Are these checkpoints independent from each other? Or do they store the system state in differencing images? If so, how would we merge them?

To keep or restore a vm from a backup, would it be sufficient to backup that one relevant checkpoint and the relevant configuration file only?

To store a backup, does it matter if the vm is in SAVED or OFF state?

thanks in advance
Gerhard

In the end, checkpoints are more like restore points. They are incremental in nature.

You just select a checkpoint and hit apply, and pc reverts to that state.

I am not certain, but if you backup the vm, using export or share option, it will save base image and all checkpoints as well. I will test this to find out. I do not think yiu can save one checkpoint.

You can of course choose checkpoint you want as final state and delete others, and all checkpoints prior to one you select will get merged. Later ones will get thrown away as far as I can tell.

GalaxyGe said:

interesting observations!

My question came up when I was reading about the Snapshots used in VirtualBox, where somebody stated it was not a good idea to build on too many checkpoints as it would be difficult in a disaster case to restore the final state from the base + the following incremental ones.

Hyper-V allows to delete any of the checkpoints, even the first one, but it still may be requiring to keep all of them, except if it explicitly does a merging when it deletes one?

Anyway I will backup the whole set, but I did realise that some of my vms through this consume huge amounts of disk space..

EDIT: Yes I tried and saw that export copies all check points, just sorted by vm instead of chunked into just one directory.

You can safely delete any checkpoint - you just cannot revert to status as of at that point when it was taken.

BTW, I use the share vm option rather than export vm as a backup.

You click on share icon on the vmconnect screen. This basically exports vm and vhd in a .vmcz file which is in fact just a good old fashioned zip file. You can even rename as .zip to exrract it.

This cuts storage requirement by 50% approx. Also delete any old and unecessary checkpoints.

There is a simple registry edit you nedd to do to allow these to be restored (@slicendice - please help me out here as I am not at pc and cannot remenber exactly how to do it)

Another issue is that vhds 'grow'. If you delete stuff, vhd space is not fully reclaimed. Even powershell commands are only partially effective.

I end up using minitool partition wizard free to shrink C drive on vhdx to its minimum, then copying all partitions to a new vhdx, and expanding c drive. Then the expanding vhdx is at its minimum size.

GalaxyGe said:

Hyper-V allows to delete any of the checkpoints, even the first one, but it still may be requiring to keep all of them, except if it explicitly does a merging when it deletes one?

When a Hyper-V checkpoint is deleted, it will be merged to current state of VM. In screenshot I've just deleted whole checkpoint subtree from a VM which is now merging them to base VHD:


I've been using Hyper-V since installing first preview version of Windows 8 in September 2011 . Windows 8 brought Hyper-V to workstation versions of Windows, I was immediately sold. I am one of the not too many users who really loved Windows 8 & 8.1, one major factor being Hyper-V.

My Hyper-V usage is quite extensive, more often than not I have at least one or two virtual machines running. I also use checkpoints relatively often simply because they are so practical, fast and easy to use. I have never had checkpoint issues.

Kari

Kari said:

When a Hyper-V checkpoint is deleted, it will be merged to current state of VM. In screenshot I've just deleted whole checkpoint subtree from a VM which is now merging them to base VHD:


I've been using Hyper-V since installing first preview version of Windows 8 in September 2011 . Windows 8 brought Hyper-V to workstation versions of Windows, I was immediately sold. I am one of the not too many users who really loved Windows 8 & 8.1, one major factor being Hyper-V.

My Hyper-V usage is quite extensive, more often than not I have at least one or two virtual machines running. I also use checkpoints relatively often simply because they are so practical, fast and easy to use. I have never had checkpoint issues.

Kari

It is interesting that if you delete an intermediate checkpoint, that gets merged with vhd.

In my simple example where I kept adding same shortcut and creating a new checkpoint, I could not initially fully understand how deleting the 2nd checkpoint with two shortcuts merged anything into the vhd. I then realised the vhd is dynamically changing as we go along (now point) and contains info from check point 2 making simple deletion more complicated.

I guess this shows the incremental nature of a checkpoint. Checkpoint 3 shows 3 shortcuts but the actual checkpoint simply adds 1 from previous checkpoint. So if vhd was not updated to have 2 icons, checkpoint 3 would end up only showing 2 checkpoints (1 from checkpoint 1 and added one from checkpoint 3).

It took me a while to realise that once checkpoint 2 was deleted, you are only ever going to change to status of other checkpoints or final state ie the merging of the deleted checkpoint is only an intermediate step to keep the 'accounts balanced" for want of a better metaphor.

Using my Macrium analogy, the checkpoints are more like the chain links of incremental backups but clever enough to handle the deletion of an intermediate incremental link.

With Macrium once an intermediate incremental link is deleted, all subsequent incremental links are useless.

If checkpoints did not do this, each checkpoint would have to be cumulative (like Macrium differentials).

So, checkpoints are really clever imo!

GalaxyGe said:

The output in PS provides perfect insight into how Hyper-V keeps track. We can see always the "Parent" for each of the snapshots.

PowerShell really is a nice tool to be used with Hyper-V.

I see you had used default checkpoint names. I like to rename mine to better remember to what point any checkpoint takes me.

Earlier today I recorded video to be sent to Macrium support. I've had contact with them because an issue with Macrium Reflect CBT and Image Guardian features; they simply break OneDrive Files on Demand feature (OD FOD) in Insider builds 17035 and 17040. To demonstrate it I clean installed W10 on a VM, then reproduced the issue creating checkpoint after each step:


I like doing it so, making a relatively short video now by applying checkpoints one after another, capturing those few seconds from that step I want to show, then applying next checkpoint and so on.

Renaming checkpoints with descriptive names tells me exactly which checkpoint I need to / want to apply.

Kari