How much time a file needs to be on disk to be in the backups forever

Hi, Let’s say I have the following backup retention: 7D:1D, 3M:1W, 2Y:1M, 99Y:1Y
and add a file to my PC. how much time do I need to keep the file on my PC to make sure it will be in my 99Y retention period?
Is it 1 Year or I just need to have it backed up once (i.e. I have to file for only a day on my pc)?

I’m trying to figure out if it is safe if I delete files on my pc (to free up some space) and be able to recover them later on.

Thank you.

I believe it would need to be on your system for >1Y to be certain that it will be retained for 99Y.

Less than 1Y - it’s possible that it might be retained for 99Y if you got lucky. Basically for the 99Y retention period only 1 annual backup is selected to be retained. If that file just happened to be in that 1 annual backup, then you’d be ok. But I doubt you want to leave it up to chance like that.

Some other backup programs have a special retention rule specifically for deleted items. I remember CrashPlan would let you choose to retain deleted items forever.

As far as I understand, Duplicati retention doesn’t currently look beyond the backup set level when processing retention rules. (In other words it doesn’t look inside the backup set at individual files…)

Great reply, but I’m nervous about the proposed usage because of a mismatch with design and stability level.

Regardless of settings, my personal belief is that Duplicati is a backup product, not an archiver, meaning it’s not designed to hold your only copy in an archive-delete-maybe-pull-out-again workflow (and I know you need space. Sorry). The UI isn’t designed for that, and the (still in beta) stability level means a data loss may occur sometime. Forever is a long time. You probably don’t mean that literally, but long-term just has more loss risk.

So I guess that if you want to keep your delete files forever you would need to have some backup retention like “99Y:1D”

btw, is there a something else than “99Y” that would mean “forever”?

For all except maybe some early canary releases, “U” means forever for a time frame (left of the colon). There’s now also an implied delete at the end of the largest time frame, so 99Y means delete after that.

Test smart retention policy #3008 describes the change, and technically “U” is a tidier way than “99Y” to specify the time frame for the interval 1Y or 1D to the right of the colon is applicable for a very long time.

The option manual doesn’t reflect any of this yet, and the online help only captures about 2/3 of it.

If you used “U:1D” then keeping the file in the source for at least a day (and running a backup of it) would mean that one per day would be kept, and this rule about intentional “thinning” applies forever. But it may wind up preserving a lot of junk that came and went that you don’t want along with things you might want.

If you’re determined to archive-and-delete in spite of the risk of losing the archive as enough time passes, then you could use a special area of the source drive that only gets lower-value files that you want saved.

The find command and maybe DIY record-keeping can help you find files later, because what’s seen in a given backup version is what was in source then, so a given source file may only be seen in one version.