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Does defragmenting a hard drive that is being backed up by image make the image grow?

I heard from a co-worker that defragmenting a hard drive that is being backed up through an image can make the backup grow. I personally don't see how this is possible due to the fact that defragmenting just rearranges files vs. changing them. Does anyone know if there is any truth in this?
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So if I run a full backup, all of the backups following could have this problem until another full backup is ran?
What do you mean, all of the backups following? Do you mean incremental ones?

If you ran a full backup while a drive was defragmenting, the data integrity on that particular backup could be compromised. The next backup would "fix" this, because all differences would be backed up. That is, the backup itself would be irreliable, but the incremental ones based on it would be reliable.
To further explain my point:

Imagine you have files A, B and C. Suppose the full backup copied A, B and a copy of B. When you run an incremental backup, it will store C and the information that copy of B isn't there anymore. When you restore it, it will restore A and B from the backup and C from the increment.
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So you are basically referring to defragmenting during the backup, not before or after a backup (image). Let's say I have a scenario where I was doing a full backup once a week with differentials once a day. Would doing defrags any time throughout the week cause the image to grow or lose data? As long as I run each separately I should be ok correct?
No, that wouldn't make any difference. At most, it would change the file position references.
Also, note that defragmenting while creating a backup would only have any affect if it was a full hard drive image. If it was just a folder backup (like C:\Docs), then it would make no difference whatsoever, because the backup would be done using a file list and not hard drive sectors.
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Awesome Cluskitt thanks for the info!
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Thanks for answering multiple questions in order to get mine anwered!
Glad to help :)