Question Backup drive almost full but computer HDD almost empty ?

[Shubert]

I'm backing up with Arcronis True Image to my Western Digital backup drive. Both have 1TB storage capacity. My internal computer hard drive is only 1.2% full but the external backup drive is 70% full.
I don't get it. I don't even seem to be able to delete anything from the backup drive.

 

[CountMike]

I'm backing up with Arcronis True Image to my Western Digital backup drive. Both have 1TB storage capacity. My internal computer hard drive is only 1.2% full but the external backup drive is 70% full.
I don't get it. I don't even seem to be able to delete anything from the backup drive.

Which kind of backup are you doing ? Cloning or classic backup ? It's probably just making another full disk backup every time so multiple backups.
Can you show snap of Disk management and file manager? As for "not be able to delete anything from the backup drive". Backup SW usually protects backed up files so to delete them you have to do it thru program that made them in first place.
Best way to backup disk, partition or folders/files is to make one full backup and next ones to be Incremental or Differential which are much smaller. Then you can keep just certain number of those (usually 1 or 2 ) and older ones get merged with main backup at set intervals.
Better backup programs like Hasleo (free) or Macrium Reflect can do that automatically as you set them.

 

[Misgar]

I'm backing up with Arcronis True Image to my Western Digital backup drive.

I do hope your Western Digital drive isn't your only backup strategy. If Ransomware strikes, it might encrypt both drives. It's a good idea to save important data to at least three different devices and never have them all connected together at the same time.

If the Western Digital drive is an external 2.5" or 3.5" spinning disk in a USB enclosure, treat it with caution. If you knock a USB hard drive over when it's running, a head crash could reduce the disk to junk.

 

[Ralston18]

@Shubert

Update your post to include full system hardware specs and OS information.

Include PSU: make, model, wattage, age, condition (original to build, new, refurbished, used)?

Disk drive(s): make, model, capacity, how full?

List of all connected peripherals.

Also, as mentioned by @CountMike, open the Disk Management window and expand so all can be seen and read.

Take a screenshot and post the screenshot here via imgur (www.imgur.com) > green "New post" icon.

My thought is a buggy, corrupt, or mis-configured backup process.

 

[cruisetung]

Turn on show hidden files in Explorer.