VSS leftovers after image restore | comparison v4.9.5 vs. v5.0.0 beta

[al3x]

Hey there,

I have a scheduled task that automatically runs a snapshot of c:\ twice a day. Command is:
wmic shadowcopy call create Volume='C:\'

Windows then stores these snapshots in C:\System Volume Information.
This enables the "Previous versions" feature in Explorer to be able to go back to an older version of a folder/file.

But what happens with those files on an image backup/restore scenario?

I tested different scenarios, here are the results:

--------------------------------------------------------------------------------
1. Image backup with HBS v4.9.5:

Behavior:
- All files in C:\System Volume Information are copied and kept in the image backup.
- On restore those files will be recreated but as empty 0-byte files.

Result:
- Restored Windows will not have Previous versions available in Explorer.
- No additional space is wasted in C:\System Volume Information.

--------------------------------------------------------------------------------
2. Image backup with HBS v5.0.0, VSS files filtered out (default):

Behavior:
- VSS files in C:\System Volume Information are NOT copied in the image backup.
- On restore those files are not available, no empty 0-byte files.

Result:
- Same as with HBS v4.9.5

--------------------------------------------------------------------------------
3. Image backup with HBS v5.0.0, VSS files NOT filtered out:

Behavior:
- VSS files in C:\System Volume Information are copied in the image backup.
- On restore those files are restored as well.

Result:
- Unfortunately Windows will NOT use those restored VSS files but still show 0 byte usage.
- Restored Windows will NOT have Previous versions available in Explorer.
- Those restored VSS files will be kept forever, resulting in less space available on C:\

--------------------------------------------------------------------------------
4. Image backup with Macrium Reflect v8.1.8311:

Behavior:
- Same behavior as scenario 2 (HBS v5.0.0 with VSS files filtered out)

--------------------------------------------------------------------------------

So what do these tests show exactly?

I think the default behavior of HBS v5.0.0 (scenario 2) is perfect, as those files are not backed up anymore. This is also the default in Macrium.
If you change that filter option in HBS v5.0.0 and you keep VSS files (scenario 3), this will result in permanently wasted space after restore.

(?) For scenario 3, Windows will not use those VSS files after a restore anyway. So if the user removes that filter option this should maybe trigger a warning for the user? Or maybe this option should not be removable at all?

If Windows could be somehow convinced to reuse those snapshots in scenario 3, this wouldn't be a problem at all. But this is probably impossible..?

[admin]

Hey there,

I have a scheduled task that automatically runs a snapshot of c:\ twice a day. Command is:
wmic shadowcopy call create Volume='C:\'

Windows then stores these snapshots in C:\System Volume Information.
This enables the "Previous versions" feature in Explorer to be able to go back to an older version of a folder/file.

But what happens with those files on an image backup/restore scenario?

I tested different scenarios, here are the results:

--------------------------------------------------------------------------------
1. Image backup with HBS v4.9.5:

Behavior:
- All files in C:\System Volume Information are copied and kept in the image backup.
- On restore those files will be recreated but as empty 0-byte files.

Result:
- Restored Windows will not have Previous versions available in Explorer.
- No additional space is wasted in C:\System Volume Information.

--------------------------------------------------------------------------------
2. Image backup with HBS v5.0.0, VSS files filtered out (default):

Behavior:
- VSS files in C:\System Volume Information are NOT copied in the image backup.
- On restore those files are not available, no empty 0-byte files.

Result:
- Same as with HBS v4.9.5

--------------------------------------------------------------------------------
3. Image backup with HBS v5.0.0, VSS files NOT filtered out:

Behavior:
- VSS files in C:\System Volume Information are copied in the image backup.
- On restore those files are restored as well.

Result:
- Unfortunately Windows will NOT use those restored VSS files but still show 0 byte usage.
- Restored Windows will NOT have Previous versions available in Explorer.
- Those restored VSS files will be kept forever, resulting in less space available on C:\

--------------------------------------------------------------------------------
4. Image backup with Macrium Reflect v8.1.8311:

Behavior:
- Same behavior as scenario 2 (HBS v5.0.0 with VSS files filtered out)

--------------------------------------------------------------------------------

So what do these tests show exactly?

I think the default behavior of HBS v5.0.0 (scenario 2) is perfect, as those files are not backed up anymore. This is also the default in Macrium.
If you change that filter option in HBS v5.0.0 and you keep VSS files (scenario 3), this will result in permanently wasted space after restore.

(?) For scenario 3, Windows will not use those VSS files after a restore anyway. So if the user removes that filter option this should maybe trigger a warning for the user? Or maybe this option should not be removable at all?

If Windows could be somehow convinced to reuse those snapshots in scenario 3, this wouldn't be a problem at all. But this is probably impossible..?

Thank you for your suggestion, we will prevent users from removing this filter option until we find out why Windows is not reusing the restored VSS snapshot files.

[al3x]

Thank you for your suggestion, we will prevent users from removing this filter option until we find out why Windows is not reusing the restored VSS snapshot files.

Sorry in advance for reviving this old thread.

But with the recent small tests I did here maybe this behavior changed in Windows and/or HBS?

When I experimented with those VSS snapshots last year, I was still using Windows 10 for my tests and also an early beta version of HBS 5.0. Now if you disable filters entirely in more recent versions of HBS (and at least with Windows 11), it seems to also perfectly restore snapshot information with image restores. Maybe this is because of changes in Windows, but maybe you also did something in HBS.

What I'm trying to say: Maybe the delete option for those predefined filters could be enabled again (if more tests show it's working now)?
That way, filters don't have to be disabled completely if you wish to keep snapshots inside the image.

[admin]

Thank you for your suggestion, we will prevent users from removing this filter option until we find out why Windows is not reusing the restored VSS snapshot files.

Sorry in advance for reviving this old thread.

But with the recent small tests I did here maybe this behavior changed in Windows and/or HBS?

When I experimented with those VSS snapshots last year, I was still using Windows 10 for my tests and also an early beta version of HBS 5.0. Now if you disable filters entirely in more recent versions of HBS (and at least with Windows 11), it seems to also perfectly restore snapshot information with image restores. Maybe this is because of changes in Windows, but maybe you also did something in HBS.

What I'm trying to say: Maybe the delete option for those predefined filters could be enabled again (if more tests show it's working now)?
That way, filters don't have to be disabled completely if you wish to keep snapshots inside the image.

Thank you for your detailed testing and feedback and for sharing these new findings from our previous discussion. This is very valuable.

The behavior you observed, where VSS snapshot information can be retained during an image restore in the updated HBS and Windows 11 environment without completely disabling filters, is indeed very interesting. This suggests that the underlying system behavior may have changed.

Regarding your suggestion to re enable the option to delete those predefined filters, our development team will conduct further in-depth research.

We appreciate your insightful testing and your enthusiasm for driving product improvements. If you have any other findings or questions during this process, please feel free to let us know.