Hard drive back up help.

[Nobbo91]

Hello I have two external hdds that are the the exact same model and I use them as a back up.

Anyways I copy and pasted all my data from 1 hdd to the other and when it was done there is 10 gig difference left in space but when I select all folders on each hdd they add up to the same amount of space.

Any ideas 10 gig difference seems a bit much.

Thanks

 

[martinch]

Probably hidden system files like the hibernation file and paging file - they're typically each around the amount of RAM you have in size.

 

[Ra_V_en]

Hidden files?
If it's not system drive then most likely it's two of those folders that might be involved:
- System Volume Information
- $recycle.bin

If not then also those drives might have different block size of the partitions so the same files might "weight" different or one of the partition has some messed journaling. Both are quite visible on system partitions or those with large amount of small files.
To check block size run such: click start -> type cmd -> run as administrator -> type fsutil fsinfo ntfsinfo [drive letter], example: fsutil fsinfo ntfsinfo c:
Compare bytes per cluster size and bytes per sector size.
To check if there is journaling issues run cmd same as above then -> chkdsk [drive letter] /x /f. If the drive is locked it will tell you it will run on the next restart. After chkdsk is done there should be no issues with ntfs journaling, also there is some information about used space... look closely there is indexes, systems files, etc info. You should now see what is hogging the space.


Edit: With FAT systems the structure was quite simple, you had generally 2 tables (FAT #1 and FAT#2) with links to the actual files (#2 was a copy of #1 in case of errors) there was some root directory space and some reserved space and data space. Generally copy of the same data took really the same space.
With NTFS it's quite more complicated.
You have some reserved space, Master File Table and MFT backups and then the data space.
In the MFT there is lot more information than in FAT, MFT contains logs, indexes, security descriptors, etc. All that makes NTFS more secure, more reliable and faster.
The thing is, after some time with much of deleting and copying that MFT is getting bigger. In fact due to this aging effect the same data just copied to another drive WILL take a lot less space, since the MFT is fresh and doesn't contain all the logs and backups yet.
I hope that will you give idea of what also might be happening in the back stage, but 10 gig is quite suspicious certainly NTFS metadada might be a part of this space.

 

[Nobbo91]

Okay but so its nothing to be worried about then. I can be sure I have the same data on both hdds regardless.

Thanks