Confused with "Keep backups" options

Hi Duplicati
I was pointed to Duplicati as a and by another Syncthing user.
Now I’m in the process of setting Duplicati for 2 friends of mine.
For the simplest one which doesn’t use Syncthing, I just want to setup Duplicati as a replacement for a broken Windows 7 backup on his W10 laptop I just repaired (local backup to the internal 2nd drive (yes drive, not just another patition)).
At the time of selecting the option for the “Keep backups” parameter, I’m stuck, mainly because I can’t figure what backup means went it come to delete backups. Maybe one could direct me to some reading about that.
I understand a backup software cannot distinguish between intentional file deletions (which should not be kept in backups in any way) and accidental (or nasty) file deletions we do not immediately notice and take immediate appropriate measures to restore (from Trash or Backup). To handle those last there may be years until we notice they were lost. So what is the better way ? Also I see there are options that refers for explanation to Daily/Weekly/Monthly/Yearly backups. Does it mean we have to set several backups in the case we don’t want “Keep all backups” ? Or would the only way be to answer the question “How many time (years) do I grant to myself to notice some files are missing” ?

[EDIT]: Please what do I miss ? When “Keep backups” is set to “Delete backups older than”, the helper text shows “If at least one more recent backup is found, all backups older than this date are deleted” :question: . I thought deduplication prevented more than one backup.

Sorry if my wording is puzzling you, I feel even more puzzled after I wrote this post :frowning:

Thanks for tips or comments.

Hello and welcome to the forum!

This is really the key. If you are only keeping backups for at most one year, and you only discover a file is deleted MORE than one year after it was deleted, you won’t be able to restore it.

Because of that, I choose to keep backups basically forever, but I do use the Custom Backup Retention option to “thin” out the older backups. I do this so that Duplicati has fewer backup versions to manage, but also to help reduce back end storage costs a bit.

My normal backup schedule runs every 4 hours, which means I have 6 backups per day. Only the most recent week keeps all 6/day backups. After that it gets trimmed to just 1/day. And then when they are 3 months old it gets trimmed to 1/week. When they are a year old it gets trimmed to 1/month. My thought is I’m more likely to want to choose among more backup versions within a small time window only for very recent backups, and the farther back I go in restores the less that granularity is important to me.

Only you can answer what your ideal settings should be. It’s a combination of your needs, risk tolerance, desire to control back end storage costs, and other variables.

Does this help at all?

Hi @drwtsn32, sorry for so late reply, I was in exam.
Thank you for long reply and Yes it helps … a bit, although it raises other questions. Unfortunately I have no more the friend’s windows PC and my Linux has something broken that prevents mono to install :frowning: so I’ll speak from memory of the GUI and from today extensive reading of the Doc, Man, and Articles.
You setup is interesting but it has 2 settings that are too paranoid for me : 6B/day and Keep4ever.
To help me to understand, would you tell me you reached this with a single Backup/Config/Schedule + the use of the blank field for “Keep this number of Backups” when one click on Custom (AFAIR there were the 3 options shown in the doc (§General options) + Smart + Custom ) ?
What are “backup versions” I read in your post ? Is it anywhen a new duplicati..dlist.zip is created which happens when a local source file is found missing/new/moved-renamed, then the Version number is increased by 1 ?