Recently, I purchased two 3TB external HDDs for backup and storage of my GoPro video files. Both drives will contain identical content. This way, when one of them fails, I can simply buy a new 3TB, or larger, drive and mirror it to the remaining intact drive. If the drives fail within 5 years, I'm covered by the norwegian customer protection laws, so I will get new drives for free I partitioned both drives into two partitions; one being 500GB and the other being 2.5TB. The 500GB partitions will be used for backing up my internal 500GB SSD. The 2.5TB partitions will be used to store my GoPro footage. All partitions were formatted in HFS+ Journaled. My problem now is that a large chunk of my SSD space is devoted to "Backup" (Norwegian: "Sikkerhetskopier"). What I have done so far: Time Machine backup, to both new external HDDs (to the 500GB partitions) Copying my internal SSD video folder to both new HDDs (to the 2.5TB partitions) Copying some more old video files from an old external HDD to both new HDDs (to the 2.5TB partitions) Deleting the old video folder on my internal SSD Why is such a huge chunk of my internal SSD filled with "Backup"?