Does "Keep backups for xx days" count by number of backups or number of days?

[akagumo0]

Maybe a bit of a dumb question, but the option to "Keep backups for xx days" has an additional note next to it stating "excluding days with no backup".

If I set this value to 100 and plan to take weekly backups (i.e., the "Daily" backup is scheduled only to run on Mondays, which effectively makes it weekly), how does that work? Does it count 100 days like you would expect based on the wording of "days", or does it keep 100 "backups", since it only runs once per week?

Due to the wording of days, I would naturally assume that setting the value to 100 means that any backups older than 100 days are removed. However, due to the extra line of "excluding days with no backup", I would assume that 6 out of every 7 days are ignored, meaning that the true value is any backups older than 700 days are removed. This is a pretty significant difference, so I was just looking for a bit of clarification on this.

Thank you.

[Gostev]

It's a good question actually! I really enjoyed "reverse engineering" our train of thoughts from a few years back.

I'm certain the number of backups does not matter, so under no circumstances it should try to "keep 100 backups".

But the "excluding days with no backup" logic also has an interesting impact that does not make the answer binary. While I forgot all implementation details, I still remember the reason for this logic, since it was added on my request. The whole idea was that you won't be left without earlier backups if your computer was turned off for longer than your retention policy. For example, if you keep backups for 10 days, but your computer was off for a month during your vacation, then without this logic you would loose all your rollback points immediately after the first backup run.

From this, I can deduce that the answer will depend on whether you computer was running each day in the past 100 days. If yes, then all backups older than 100 days will be removed. If not, then only backups older than (100 days + number of days when the computer was off in the past 100 days) will be removed. But I will want the PMs to confirm this with R&D!

[joachimeberhard]

Hello.

I currently have the same issue.
I have automatic backups configured for client machines that are most of the time disconnected from the network, and all of them at different times.

Wouldn't a logic, that simply works like "keep at least 30 days *AND* (EDIT: or maybe technically "OR") 30 retention points be much more useful for "real-world" scenarios?

I already have a case where a very important backup was gone because the client never connected in "the right" time defined by GFS.