Incremental backup replacing modified file from the complete one

[emanuell2]

Hi everyone, I've been using cobian backup for sometime now for my backup needs and i've been using 1 complete backup once a week and incremental backup everyday, the thing is that my files have grown a lot so I fear that the complete backup (in a 4 tb wd black) shorten the lifespan of the disk, so the question as the title says is, it's possible to create 1 complete backup and do incremental backups everyday but replacing in the complete backup the modified file so it doesn't grow larger everyday? Is there a software capable of that I wasn't able to find it.
Any answer will be appreciated. Thanks in advance.

 

[Solandri]

That is basically what an incremental backup is.

Differential backup: Full backup made one day. Every following day, differences between that day's files and the full backup are backed up.

Incremental backup: Full backup made one day. First following day, differences from the full backup are backed up (same as differential). Second following day, differences from the previous day's incremental backup + full backup are backed up. Each following day, any files which have changed from the file state of the previous day's incremental backup + previous backups is backed up.

Basically, differential backups backup files which have changed since the full backup. Incremental backups backup files which have changed since the previous day's backup.

Differential backups grow in size every day, becoming bigger the longer it's been since your full backup. So a full backup every week is warranted. The advantage of doing it this way is that recovering a file depends on only the full backup and the most recent differential backup. If the intermediate differential backups are corrupted, your files are still safe. Another way of putting it is that the differential backups in between the last full backup and the previous day's differential backup are unnecessary and can be deleted.

Incremental backup size does not depend on how long it's been since the last full backup. You can change the full backup to once a month with incremental. I've even seen once every 3 months, but that starts to get risky. With incremental backups, the file you need to recover could be stored in any one of the incremental backups. So there's a greater risk of backup corruption the longer it's been since your last full backup. Another way of putting it is that the only unnecessary data in an incremental backup is backups of files which have since been overwritten. Unfortunately this data is scattered throughout the full and incremental backups, so you can't delete any of the intermediate backups. The only way to "reset" it is to create a new full backup.

Edit: You could switch to doing an rsync for backups. Basically you make a full backup. Then every day your computer compares the checksums of every file vs the checksums of backed up files. Any file which has changed gets updated in the backup. Unfortunately, this loses one of the benefits of backups - ability to go back to a previous version of a file. e.g. If your computer gets hit by ransomware and does a rsync backup, it'll replace all your good backup files with ransomware-encrypted files and your backup will be useless. With differential or incremental backups, your pre-ransomware versions of your backed up files are still around (assuming the ransomware hasn't encrypted your backups).