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Question

Calculator seems off for S3 Immutable GFS Backups

  • December 9, 2025
  • 0 comments
  • 19 views

Hello guys,

 

I’m using the Calculator on a daily basis, and am pretty sure the calculation is wrong (or maybe I’m?? :D) when you consider Immutable GFS Backups to Object or local storage.

If you backup Immutable the Calculator will ask for a immutability Period, this in fact does not matter when using GFS as always one Full Backup will be kept for the configured GFS Retention.

Or at least as far as I’m aware.


Heres my test:
Lets say we have 16TB of source Data, this is the immutability with 14 days and gfs.
​​​​​​

 

As far as I understood it, 16TB is round about the source capacity, of course we will shrink it a bit thanks to compression.

Lets say a full backup will then be 10TB which seems surreal already. And lets now turn gfs off in the calculator.

Now we only have 14 Dailies immutable but we are missing another 11 Full Backups as stated, GFS will always take full backups.

 

Am i doing something wrong? Is the calculator not able to predict this scenario?