Giant differential

[lazyguy]

Hi!
I have problems backing up one of the partitions on my hard discs. It's one of those that don't change very often, so I made one complete backup image on DVD and now that some changes occured on this particular partition, I decided to make a differential.
It has a capacity of 80GB, and at the time I made the complete backup, there was about 22GB used. Now, it is about 27GB with none of the old files changed. Oh and one more thing to explain: since direct DVD recording was not supported before build 3.641, I got used to leaving a copy of the last part of any complete backup on my backup drive (internal HD) and creating any differential backups based on this last part. This works perfectly fine on every other partition...
However, on this one it doesn't. The operation of creating a differential is cancelled every time for the backup partition is full. Before, there is about 10GB of free space.
So as you see, the differential would get really big, if it came to an end. I know that TI includes any changed sectors into the differential, but ending at a size of 10GB with indicating 20 mins left seems an awful lot to me for only 5GB that I changed by myself...
Of course I could make a complete backup from time to time, but this would take a lot of time, so I don't really want to do it this way.
Can anyone imagine, why the differential (only) on this particular partition gets that huge? It works perfectly fine on two other partitions and as well when backing up some files only (not a complete drive).

OK, I hope some of you understood this ;)
If you need any more info, just ask... Thanks!

[Menorcaman]

Hello lazyguy,

Have you defragged that particular partition or copied, moved, added and then deleted many of the files? If so then the thumb print of the used sectors will be very different to that of the original full image. Hence the differential can end up almost as large as the full.

Regards

[lazyguy]

Well first of all, thanks for your answer...
Yes, I indeed had some temp stuff on that drive and later deleted it again. But I'm not quite sure if that was before or after I made the full...
Anyway, seems I have no choice and have to make a new full. Restoring the old full while keeping the new stuff somewhere else, then moving it back and make a differential - hm, not good, stupid...
Overwriting unused sectors with all zeroes - even more weird, this would result in a 80GB image I guess!?
Whatever, a new full seems to be the easiest way...

[shieber]

ATI is sector based, if you cahnge the secotrs, you get a diff map to be copied/cloned/imaged. Even if you deleted a file and copied it back, it wouldn't be the ame sector map, even though the data in the file is unchanged.

sh

[Acronis Support]

Hello lazyguy,

Thank you for choosing Acronis Disk Backup Software (http://www.acronis.com/homecomputing/products/trueimage/).

Please be aware that there are four most probable reasons why Acronis True Image creates too large incremental\differential images:

- Windows System Restore (http://www.microsoft.com/windowsxp/using/helpandsupport/learnmore/systemrestore.mspx) is enabled and creates restore points on a regular basis.

- Too many changes were made to the backed up disk\partition since last full\incremental\differential image was created.

- Backed up disk\partition was defragmented:

The following quotation from section 3.2 of Acronis True Image 9.0 Home User's Guide (http://www.acronis.com/homecomputing/download/docs/) explains the issue:

-{ Quote: "An incremental or differential backup created after a disk is defragmented might be considerably larger than usual. This is because the defragmentation program changes file locations on disk and the backups reflect these changes. Therefore, it is recommended that you re-create a full backup after disk defragmentation." }-

- There are some file system errors on the backed up disk\partition:

In this case Acronis True Image recognizes the file system as corrupted and creates a raw sector-by-sector image of the backed up disk\partition. The size of the resulting image will be equal or almost equal (depending on the compression level you selected) to the size of the backed up disk\partition. Please see this previous thread (http://www.wilderssecurity.com/showthread.php?t=112864) for details.

Whatever the actual reason is, we recommend that you check each partition of the backed up hard drive by Windows utility in the following way:

- For Windows 9x please use Windows menu Start\Run then enter the command "scandskw" and test all drives;

- For Windows XP please use Windows menu Start\Run, then enter the command "chkdsk c: /r" "chkdsk d: /r" for every partition of your hard drive.

Note that you will need to reboot your computer in order to scan the system partition.

We also recommend that you turn off Windows System Restore as it is described in section 10.3 of the above mentioned User's Guide.

Then please re-create the full image anew and proceed with creation of incremental\differential images.

If the problem appears in the future then please provide us with the following information:

- Create Acronis Report as it is described in Acronis Help Post (http://www.wilderssecurity.com/showthread.php?t=55317);

- Let us know the exact size of the actual data contained on the backed up disk\partition;

- What is the exact size of the initial full image?

- What are the sizes of the subsequent incremental images?

- Where do you store these images?

Then please submit a request for technical support (http://www.acronis.com/homecomputing/my/support/). Provide the files and information collected in your request along with the step-by-step description of the actions taken before the problem appears and the link to this thread. We will investigate the problem and try to provide you with the solution.

Thank you.
--
Alexey Popov