Cloning and Differentials


I’m wanting to clone my C: drive to an external one and make regular differential backups using the clone as the basis , and have some questions. I’ve been trying to educate myself through the CB forum and other online resources, etc., but I don’t feel confident I have considered all the necessary angles.

Regarding the cloning, my overall goal is to (if possible) simply exchange my external drive for the primary drive in the event the primary drive dies.

  1. My primary drive is 750 GB (only 135 GB used) and my external drive is 500 GB. From another posting, I understand that I need to create a partition for the C: drive of 500 GB or less to be able to clone it to the external drive. Is this correct? Do I use a 3rd party software to create the partition?

  2. Can differential backups then be made using this clone as the basis? If so, is it a relatively quick process where CB just checks for differences to the clone and makes those changes? (The reason I ask is that I tried Paragon, and the first differential to the clone (which consisted of only a very small change to a single Excel file) took 7 hours to complete, as long as the original clone took to make!)

  3. In the event my primary drive dies, from what I understand, I would use a BartPE (or WinPE) to restore from(?) In my scenario described above, this would leave me with one drive, the external one with the clone and differentials on it. In this case, can I simply switch out drives and use the external one as my primary drive, or do I need to copy its cloned contents onto yet another drive? In other words, does the BartPE simply get the hardware talking to the clone on the external drive, setting things up again as though it’s the new primary drive, or only allow me to access the clone and copy it to another drive?

  4. Do all files get copied when you perform a clone? (If so, where do I indicate that I want this?) I have concern I’ll lose some background settings that are important to me or are a hassle to reconstruct. Also, it says that when you do a Bart PE , you lose your registry settings. What is the practical impact of this?

Thanks for any and all of your efforts!

Also, if it’s relevant, I have Windows 7 Professional 64-bit, an AMD Athlon II quad processor, and 6 GB of RAM.


    Yes, you could use third party software or go to Control Panel -> Administrative Tools -> Computer Management -> Disk Management. 
       But, Since you have Windows 7, cloning C: drive to your external will not make the external drive bootable in case of a computer crash because Windows 7 also needs system reserved drive (which is visible in Computer Management), MBR and disk signature.
  Cloning is a full sectory-by-sector copy from source drive/disk to destination drive/disk. So probably it will take the same with CB.
   Only CBU-file backups can be incremental/differentials.
      Cloning the C: drive to your external will mirror the C: drive [b]as it is[/b] to external and overwrite any existing files on external drive. There won't be any differentials on it.
      BartPE/WinPE rescue media only allows you access to the clone.
      All the files get copied when you perform a clone. You might have misunderstood the part with registry settings. What the user guide is trying to say is that you can't restore registry-keys backups, but this isn't your case.

PS: If you use backup to CBU file, you can perform incremental/differential backups, you don’t need to resize C: and you can still use the external hard disk to store other files.


Thanks for your responses!

Since all the ins and outs of this are somewhat confusing to me, I’m going to try to ask my questions in another way.

  1. In the event of my primary drive failing, I want to be able to get my computer as completely as possible back to where it was in the simplest and quickest way, using differential backups to my external drive. Using CB, what method do you recommend?

  2. With the method you suggest above, how would the restoration be performed? Could I restore to the backup drive, or would I need a third drive (given that the primary drive would be dead)?

  3. Besides the CB backup restoration, what else would need to be reloaded? Would anything (e.g., Program File settings, key registry stuff) be lost? Would I have to manually rebuild such settings or reestablish connections between applications, etc?



I recommend you the default option, select your internal hard disk (in step 1, “Disk, Partitions and MBR”) choose differential and then in backup step 2 choose a location. You can also schedule the job.
All backups (full + differentials) will be stored in the same file, unless you set different names for scheduled backup destination.

You can use a BartPE/WinPE rescue media and restore.
See help for more details.

The machine will be restored in the exact state it was when backup was performed. So you won’t have to rebuild anything.


Hello, thanks for your response.

Since I have Windows 7 64-bit, it appears that I wouldn’t be able to use BartPE, but would need to use WinPE. I have looked over the step-by-step configuring of WinPE on your site, and it’s way beyond my current computer capability and comfort zone, having to understand and do significant programming in MS DOS.

After reading the restore info on your site, I’m still not certain whether I would need a third drive (it may state this indirectly, but in terms I don’t recognize.

Thanks for your efforts, but at this point I’m going to look for a program that can fully explain the concepts and courses of actiions/restore scenarios with enough granularity, but in way that the layperson can fairly understand.


Your answers to Greg answered some of the questions I was going to ask. But I still need some clarifications.

  1. Does CBU file stores the entire system with all the programs, OS, settings etc.?
  2. Is its content the same as a clone would be, only compressed?
  3. Is it true that I can create WinPE disk from Comodo environment with everything needed to restore my system from the CBU file?
  4. Can I create the CBU file for the complete system the 1st time, and then just do incremental and differential back-ups for all the new or changed files?




Actually, no.
To create a WinPE disk you need to follow the steps in user-guide. The rescue media will contain a bootable Windows.
This media can then be used to restore any data, just make sure you copy installation folder and run CBU.exe from other location than the restore destination.



It looks like you provide a workable method for doing a bare-metal restore from an external drive after backing up with CBU. Is this (bare-metal restore of a bootable complete system drive) also possible if remote Comodo Online (cloud) Backup has been used, rather than a local external drive?

No, unless you manually install & start COSService and set an internet connection in PE environment.


So, if I understand correctly, the answer is in fact “Yes” – so long as I “manually install & start COSService and set an internet connection in PE environment.” What remains is for me to discover how, exactly, to do that. Are instructions available? I am assuming that COSService is the Comodo Online Storage Service – but I do not know what procedure I would follow to install and start it when trying to restore to bare metal, and I am not sure what you mean by “setting” an internet connection in the PE environment. Any further help would be much appreciated! Thanks!


To install the Comodo Online Storage Service use the following commands in cmd.exe:
sc install COSService.exe binpath= “<path_to_Cosservice.exe>”
sc start COSService.exe

There are multiple ways of connecting to the internet depending of ISP.
For example, some internet connection may require an username and password to be set.
You must set the internet connection in the same way it was set on your computer.