Differential archive - what kind of animal?

Question

Backup

Hello!
Let's imagine a situation. Set up differential backup via Cobian Backup.
A complete copy was preserved, and only the modified files went on.
Let's say I change 1 file per day, in total for the year I will have 365 archives with 1 file inside. At the end of the year, the hard drive fails.
How can I restore so that all the information is up to date?
Shouldn't I unpack 365 archives and replace files in a full copy?!

Answer 1

This is not a description of differential backups, but incremental backups, and in the case of continuous incremental backups, you will need the latest full backup plus ALL incremental backups in order of creation to restore. What is not enough, you will not restore further - they form a coherent sequence. If you create just differential ones, then in each copy there will be a difference between the current state and the full backup, i.e. the first will have one file, and the 364th will have 364, if "one file per day" means different files each time. Then you'll need a full copy plus the latest differential to restore.
As for restoring 365 archives - in a good way, when you restore data, the interface prompts you to specify the date, and deploys a backup of all the necessary files. That is, this is the job of the backup system - to use the necessary files for recovery, the operation in any case will be the same on the part of the user. By the way, do not forget to back up the database of Cobian itself, otherwise, before restoring, you will have to re-read them all just to understand which file stores what.

Answer 2

You will need two archives.
If you have a differential archive, you will need two archives - full and differential on the desired date.
The differential archive contains all changes since the creation of the full archive.
If you had an incremental backup, then you would need the full backup and all incremental backups up to the required date to restore.

Answer 3

Differential = differential. Saves files that have changed since the last full backup. In your case, in order to recover from a differential backup, you need to restore the latest full backup and roll the last differential backup onto it.