Why is my diff backup so large?

Gurus,

I've just done a full backup on my Boss' laptop using True Image Home 10. The full backup came in at around 14gb. Now, two days later, I've gone to run a differential backup, but it is telling me the estimated backup size is about 14gb. Why is this? This is the same experience I had when I ran an incremental backup; that file size was slightly larger than the base image!

Please advise, and thanks for your time.

-Michael

 

Was a defragment run on the drive between the FULL and the DIFFERENTIAL backups? If so, then that's the most likely reason.

TI goes by the used sectors. If the sectors have moved then TI sees them as changed and backs them up again.

If this is the case, then schedule (or manually run) the defragment before you do your Full backup and then don't run another defrag until before your next full backup.

 

Hey MudCrab, thanks for getting back with me.

I did not do a defrag on the machine. I made the base image, running it to an external USB HD. Two days later I ran an incremantal backup, and like I said the filesize was actually slightly larger than the base. I went Acronis' website and researched backups, and the differences between them. Decided to see what would happen with the differential, and it said the filesize would be about the same as the incremental.

Maybe I should just make a new base image?

-Michael

 

Some of us only make full images, and this is part of the reason.

Did you check to be sure your Boss' computer doesn't have an automatic defragging program running or something else unusual such as full disk encryption?

 

Hi John,

There is nothing else running. It's actually a totally clean install of XP Pro, was about 5 days old when I made the image.

He works almost exclusively from home. I was hoping to get it set up so that I could keep the base image at the company, and every night have his differential backup run over the VPN. That will entirely depend of course on what the filesize ends up being on average.

 

Incremental: All of the data that changed since the last full or incremental if there is one (there isn't so it is based on the full).

Differential: All of the data that changed since the last full.

The first backup after the full whether or not it is an incremental or a differential contains the same data.

Unfortunately, this doesn't solve the original question as to why they are so large. I don't do incremental or differentials so I can't be of much help.

 

Have a look at this thread. If you are running Vista note the last post in the thread about the the defragger.

https://www.wilderssecurity.com/showthread.php?t=170645

 

Perhaps the second backup was also a full baclup and not a differential as you intended. Use the Mount Image wizard to select the backup file and see if it's identified as "Volume 2 of Multivolume image".

 

Thanks SloPoke, I'll check it out.

-M