So I did a full backup

...and the backup takes up more space (377GB) on the external HDD, then my system uses on the internal HDD (344GB). What did I screw up? I always thought backups were done with compression, and took up less space. Why is my backup taking up more space?

Does your original HD have a different partition?

Ummmm.....


How do I check?

Sector size different between the two drives maybe.. so the new one is a 4k sector drive which means that files can potentially take up more physical space.

palmor wrote in post #14921912
Sector size different between the two drives maybe.. so the new one is a 4k sector drive which means that files can potentially take up more physical space.

This was my immediate thought...

The most common, when discussing direct HDD => HDD backup is the sector and cluster sizes of the disk, and if the file system have support for "fractions" - many small files being combined together and stored in a single larger block.

Next thing is that backup compression is quite often a fast compression that can make jpeg, zip, rar, mov, ... actually grow.

Yet another thing is that better backup program can generate redundancy information. I.e. the backup can contain error correcting code so that a broken block on a DVD can be totally recreated - this besides the ECC that the HDD/DVD/tape/... make use of for every individual block to correct limited bit errors within the block.

In the end, it isn't automatically sure that a backup is smaller than the original data.

So would I be best off reformatting the external to be sure it have the same sector sizing and partitioning, and then do the backup again?

There were also files that I backed up that I really didn't want/need to back up, so it wouldn't be a terrible thing to do it again.