backup live systems

[bliblubli]

Is it reliable to backup a read/write mounted drive on windows with wimcapture? And the system drive?

[synchronicity]

The latest beta version supports this using VSS snapshots (--snapshot argument to wimcapture and wimappend). This functionality has not yet been widely tested, however.

[Vortex]

Hi synchronicity,

Thanks for implementing the VSS snapshots. Windows XP supports VSS but wimlib 1.9.0 beta 3 displays the following error message :

Code: Select all

D:\wimlib>wimcapture.cmd C: H:\test.wim --snapshot
Scanning "C:"
[ERROR] CreateVssBackupComponentsInternal() not found in vssapi.dll
[ERROR] The Volume Shadow Copy Service (VSS) API could not be initialized. Probably it isn't supported on this computer.
[ERROR] A problem occurred while creating a VSS snapshot of "C:\".
        Aborting the operation.
ERROR: Exiting with error code 89:
       Unable to create a filesystem snapshot.

Tested on Windows XP Sp3

[synchronicity]

Currently it only works on Vista and later because Windows XP requires different code to make VSS work.

[synchronicity]

I attempted to get it working on XP but wasn't able to. I'm not going to bother further since XP is supposed to be dying.

I'll update the documentation and error messages to be more clear that only Vista and later are supported (for snapshot mode).

[bliblubli]

Ok, tested it for the first time, really nice addition :
1) First test to restore such files from Linux shows really high fragmentation of the partition. It is not the case on the original one (0% fragmentation). On different forums, they say it comes from NTFS-3g, what is your experience?
2) Wimlib reports 83 GB scanned but windows says 12.2 GB of 97.5 are free, so it should be 85.3GB ?
3) GLOBALROOT\Device\HarddiskVolumeShadowCopy1\System Volume Information and GLOBALROOT\Device\HarddiskVolumeShadowCopy1\Windows\CSC are excluded. What are those folders and could they be the missing 2.3 GB?
3) The reported size of uncompressed data reduce over times, I guess it's the deduplication?
4) Are all hidden software like copy protection/rootkits ones for games (Steam etc...) also copied ? Or could they also be the missing GB?
5) What happens to the modifications done on the partition after the copy process has started?
6) Can we restore it in windows also?
7) Compression ration are amazing! 86GB compressed to 47GB and that at the max speed the HDD can do

[synchronicity]

1. When extracting files in NTFS-3g mode, NTFS-3g is responsible for laying out the files. I don't know the details of how it does so.
2. You can't trust minor differences in size statistics because there are many different ways to compute and present them.
3. Those are special Windows folders which are on the default exclude list as they typically should be excluded from backups. The default exclude list is listed in the documentation and can be overridden if desired.
3. As duplications are discovered, the size to write decreases.
4. All files are included except when excluded by name. Attributes and security descriptors do not matter.
5. When capturing in snapshot mode you are capturing from a point-in-time snapshot that was created early in the capture process. So any later modifications are not reflected in the WIM image.
6. Yes, just use wimapply. Edit: if you are talking about overwriting a *live system* with a WIM image, that's not possible.
7. There are also options to get a better compression ratio, but it will be slower and in some cases not compatible with DISM/WIMGAPI. For example, use --chunk-size to increase the LZX chunk size; or use --solid to create a solid LZMS-compressed WIM.

[bliblubli]

for 2. I know we get 3TB HDD today for 80€, but 2.3GiB are still a lot to my eyes Are you sure it's only due to differences in size computation?
for 6. but capturing a live system works?

[Vortex]

Hello synchronicity,

Here is my project vscopy working on Windows XP. I use it together with wimlib to backup live systems.

http://vortex.masmcode.com/files/vscopy101.zip

http://www.oby.ro/forum/viewtopic.php?t=309

[synchronicity]

@bliblubli

It may seem like a lot of space, but as a percentage it isn't a lot. There are a few things that can cause a difference of multiple percent, such as confusion between power-of-10 gigabytes and power-of-2 gigabytes, or counting allocated space used on disk versus counting the total file data size.

Yes, you can capture a WIM image of a live system using the new VSS support, but there is no way to replace a full live system with a WIM image at runtime.

@Vortex

Thanks for the example code. I was able to get my code working on XP. There were a couple differences I had missed. It's a little annoying, but there are still few enough differences that it's realistic to support both.

As a result, I've posted a new BETA, which should have VSS working both on XP and on newer versions of Windows.