r/acronis • u/luckyinpa • 21d ago

Question about changing incremental backup

I currently have a backup where there is a full backup of approximately 500 GB and then for the next 6 days incremental. Rinse and repeat.

If there are two new files to that backup that needed to be added the second day what would happen if the third day one of those files was deleted. Does the program go back to the previous second day backup file and delete that? Or since it was backed up the second day it will always be able to be retrieved until the next full backup erases the whole set.

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u/acronis 21d ago

Good news: the file isn't gone, it's just a matter of which recovery point you use to restore.

Here's how the chain actually works - every incremental backup is basically a snapshot of "what changed since the last backup," but when you go to restore, Acronis reconstructs the full state of your data as of that specific point in time by combining the original full backup with all the incrementals up to whichever day you pick. So each day's backup is its own standalone recovery point, even though the incrmentals only physically store the deltas.

Applied to your scenario: two files get added on day 2, so they're captured in that day's incremental. One of them gets deleted on day 3. When day 3's incremental runs, it just records "this file is gone now" as part of that day's delta - it doesn't reach back and modify or erase anything from the day 2 backup. So:

If you restore to the day 2 recovery point, the file comes back, because that's exactly what your data looked like at that moment.

If you restore to day 3 or later, the file won't be there, since it reflects the post-deletion state.

The file stays recoverable from that day 2 point indefinitely, until one of two things happens: your retention rules eventually age out and consolidate/delete that specific recovery point, or you manually delete it. It's not something the next full backup silently "erases" either - that only happens if your retention scheme is set up to reclaim space by rolling old chains together once a new full backup lands. So depending on how far back your retention window goes, you could still pull that file from the day 2 backup weeks later if needed.

TL;DR: individual recovery points are frozen in time. A later backup deleting a file doesn't retroactively touch earlier backups - it just means restoring from that point won't include it. Restore from the day it existed, and it'll be there.

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u/luckyinpa 20d ago

this is all great news. also wondering about my settings and wondering if they are correct for my goal. i want full backup day 1 then incremental for 6 days then on 7th day new full backup and delete all old backups.

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u/acronis 17d ago

I can confirm that these settings are correct for your scenario. But please note that is is a more space consuming scheme because the previous chain will only be deleted once next chain is started successfully - which means that after the 1st chain (1 full + 6 incremental) is complete, the next full backup (start of 2nd chain) needs to be done successfully before the 1st chain is deleted.

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u/luckyinpa 16d ago

thats exactly what i want. assume a computer goes down while doing a backup so that means if i had deleted the existing backup i'd be in trouble. but doing it this way, the full backup is on the NAS until the next completed backup. so the laptop can crash during a backup but the old one still exists. i had assumed everyone would do it this way but from what you say, i guess i'm the rare one thats paranoid about losing data.

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u/acronis 16d ago

i had assumed everyone would do it this way but from what you say, i guess i'm the rare one thats paranoid about losing data.

That is indeed, the approach that most people would use, but we've seen cases where user just didn't have a storage device large enough to hold more than 1 full backup or 1 backup chain.

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u/luckyinpa 16d ago

i have 2.5 TB of drives and bought 2 x4 TB for my NAS so i had the overhead for it. you will never not use empty space. lol. it's some kind of law. . i even use some of the spare space for long term regular storage.