Make recent backups immutable for x days

[AlexL]

Hi, I've read the documentation and read the forum but still in doubt about the "best" setting for the immutability period.
We're going to do backups daily, keep 14 days, 4 weeks and 4 months. We'll be doing a full 1:1 copy to Object Storage with a SOBR, that is, check the box "copy to object storage as soon as they are created" with the "move to object storage as they age out". So far, this is what we need and want.
But, we want recent data in object storage to be immutable, question is, what would be a good enough period.
We're thinking about 7 days would be ok, but there is the 10 days that are added automatically.
So we could choose 4 days (+10 = 14), the same as daily restore points.
Or 7 days (+10 = 17 days), but are we correct this would use slightly more object storage ?
Or 10 days even, so we have 14 daily's, but up to 6 incrementals since we have the chain on the last weekly. But again this would cause (slightly) more data to be kept in object storage if I'm right?
Any suggestions, or best practices, or better yet, what do you guys actually use and why? Considering we do not have a need to have all GFS points immutable, just recent ones (one to two weeks).
Mostly interested in practical usage insights, the considerations and consequences.
Thanks a lot in advance.

[HannesK]

Hello,

but are we correct this would use slightly more object storage ?

correct. how much is hard to estimate.

but up to 6 incrementals since we have the chain on the last weekly

with 14 days, you have up to 18 increments http://rps.dewin.me/?m=1&s=1000&r=14&c= ... ,0,0,1,0&e

If you have to have one GFS point immutable, then 7 days is the minimum. Whatever more you chose is up to "how much more costs do you like to see?" As I said, it's hard to predict the costs. I would go with 7 days, because the older backups are, the less useful the are in many situations

Best regards,
Hannes