The support forum

Source vs backup size discrepancy

ng4ever :

Nov 23, 2018

With Bvckup2 one hard drive takes 1.92 TB another 1.89 TB out of 4TB. I am trying to figure out why they are both not taking the same TB space. I am very anal about this and a perfectionist. Any easy way to figure this out without redoing my backup again from one hard drive to another to see if it makes any difference ?


Alex Pankratov :

Nov 23, 2018



You will need to start by understanding what these numbers you are looking at mean exactly. It can be the "real" file size, it can be "size on disk" size or it can be something else altogether. In the second case the difference can be due to using different cluster size (assuming NTFS) or using volume compression, for example. Also, make sure that both numbers use the same definition of terabyte, i.e. that one is not calculated assuming it's 1000 bytes per K and another - that it's 1024.

Secondly, look in the backup log. Check for any errors. Check for reported sizes and file counts (it's all there). Check if you have any files excluded at source due to default exclusion rules (this will be in the "Preparing > Scanning source" section of the log).

Basically, check that file _counts_ on both sides are the same. If they aren't, check for backup errors and fix your backup configuration. If they are the same, then check what your byte count numbers mean to make sure you are comparing apples to apples.

ng4ever :

Nov 23, 2018

Thank you!

ng4ever :

Nov 25, 2018

I may have found the issue or maybe not.

Here is the sizes of both 4TB drives. One internal other external.

Weird.

Before RMAing one of the drives they use to be the same free space after Bvckup 2 was done. Now there not. by .3 TB. I guess this is why.

I wish I could fix it though. :(

https://i.imgur.com/5PfrbsH.jpg

https://i.imgur.com/HukEB1H.jpg

Alex Pankratov :

Nov 26, 2018



To me, you are approaching this from the wrong end. Start by comparing reported file/folder sizes, then compare on-disk sizes, then - disk format details (cluster sizes), check if either has bad blocks that are marked as such, etc.

But as I said, if files counts/sizes on both drives are the same, this is not something that can be "fixed" by changing any Bvckup settings.

ng4ever :

Nov 26, 2018

Ok thanks.

New topic

Create
Made by Pipemetrics in Switzerland
Support

Follow
Blog / RSS
Social Twitter
Reddit
Miscellanea Press resources
Testimonials
Company
Imprint
Legal Terms
Privacy